vmtest: TrustyTestRaid5Bcache task blocked

See:
https://jenkins.ubuntu.com/server/job/curtin-vmtest-devel-amd64/860/artifact/output/TrustyTestRaid5Bcache/logs/install-serial.log

Running command ['chroot', '/tmp/tmpbfDAu8/target', 'eatmydata', 'apt-get', '--quiet', '--assume-yes', '--option=Dpkg::options::=--force-unsafe-io', '--option=Dpkg::Options::=--force-confold', 'install', 'bcache-tools', 'mdadm'] with allowed return codes [0] (shell=False, capture=False)
Reading package lists...
Building dependency tree...
Reading state information...
The following extra packages will be installed:
  postfix ssl-cert
Suggested packages:
  procmail postfix-mysql postfix-pgsql postfix-ldap postfix-pcre sasl2-bin
  dovecot-common postfix-cdb mail-reader postfix-doc openssl-blacklist
Recommended packages:
  default-mta mail-transport-agent
The following NEW packages will be installed:
  bcache-tools mdadm postfix ssl-cert
0 upgraded, 4 newly installed, 0 to remove and 8 not upgraded.
Need to get 1480 kB of archives.
After this operation, 5040 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu/ trusty-updates/main bcache-tools amd64 1.0.7-1~14.04.1 [17.4 kB]
Get:2 http://archive.ubuntu.com/ubuntu/ trusty-updates/main mdadm amd64 3.2.5-5ubuntu4.3 [362 kB]
Get:3 http://archive.ubuntu.com/ubuntu/ trusty/main ssl-cert all 1.0.33 [16.6 kB]
Get:4 http://archive.ubuntu.com/ubuntu/ trusty-updates/main postfix amd64 2.11.0-1ubuntu1 [1084 kB]
Preconfiguring packages ...
Fetched 1480 kB in 1s (981 kB/s)
Selecting previously unselected package bcache-tools.
(Reading database ... 56532 files and directories currently installed.)
Preparing to unpack .../bcache-tools_1.0.7-1~14.04.1_amd64.deb ...
Unpacking bcache-tools (1.0.7-1~14.04.1) ...
Selecting previously unselected package mdadm.
Preparing to unpack .../mdadm_3.2.5-5ubuntu4.3_amd64.deb ...
Unpacking mdadm (3.2.5-5ubuntu4.3) ...
Selecting previously unselected package ssl-cert.
Preparing to unpack .../ssl-cert_1.0.33_all.deb ...
Unpacking ssl-cert (1.0.33) ...
Selecting previously unselected package postfix.
Preparing to unpack .../postfix_2.11.0-1ubuntu1_amd64.deb ...
Unpacking postfix (2.11.0-1ubuntu1) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Processing triggers for ureadahead (0.100.0-16) ...
Processing triggers for ufw (0.34~rc-0ubuntu2) ...
Setting up bcache-tools (1.0.7-1~14.04.1) ...
update-initramfs: deferring update (trigger activated)
Setting up mdadm (3.2.5-5ubuntu4.3) ...
Generating mdadm.conf... done.
 Removing any system startup links for /etc/init.d/mdadm-raid ...
update-initramfs: deferring update (trigger activated)
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.13.0-115-generic
Found initrd image: /boot/initrd.img-3.13.0-115-generic
done
invoke-rc.d: policy-rc.d denied execution of start.
Setting up ssl-cert (1.0.33) ...
hostname: Name or service not known
make-ssl-cert: Could not get FQDN, using "ubuntu".
make-ssl-cert: You may want to fix your /etc/hosts and/or DNS setup and run
make-ssl-cert: make-ssl-cert generate-default-snakeoil --force-overwrite
make-ssl-cert: again.
Setting up postfix (2.11.0-1ubuntu1) ...
Adding group `postfix' (GID 112) ...
Done.
Adding system user `postfix' (UID 106) ...
Adding new user `postfix' (UID 106) with group `postfix' ...
Not creating home directory `/var/spool/postfix'.
Creating /etc/postfix/dynamicmaps.cf
Adding tcp map entry to /etc/postfix/dynamicmaps.cf
Adding sqlite map entry to /etc/postfix/dynamicmaps.cf
Adding group `postdrop' (GID 113) ...
Done.
setting myhostname: ubuntu
setting alias maps
setting alias database
mailname is not a fully qualified domain name. Not changing /etc/mailname.
setting destinations: localdomain, localhost, localhost.localdomain, localhost
setting relayhost:
setting mynetworks: 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
setting mailbox_size_limit: 0
setting recipient_delimiter: +
setting inet_interfaces: all
setting inet_protocols: all
/etc/aliases does not exist, creating it.
WARNING: /etc/aliases exists, but does not have a root alias.

Postfix is now set up with a default configuration. If you need to make
changes, edit
/etc/postfix/main.cf (and others) as needed. To view Postfix configuration
values, see postconf(1).

After modifying main.cf, be sure to run '/etc/init.d/postfix reload'.

Running newaliases
invoke-rc.d: policy-rc.d denied execution of restart.
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[ 602.344119] INFO: task frontend:12688 blocked for more than 120 seconds.
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[ 722.344054] INFO: task frontend:12688 blocked for more than 120 seconds.
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[ 842.344066] INFO: task frontend:12688 blocked for more than 120 seconds.
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[ 962.344083] INFO: task frontend:12688 blocked for more than 120 seconds.
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[ 1082.344034] INFO: task frontend:12688 blocked for more than 120 seconds.
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[ 1322.344028] INFO: task frontend:12688 blocked for more than 120 seconds.
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