keyscript=passdev for keyfiles via usb does not timeout

1.) ubuntu-release
root@ubuntu-4crypt:/var/log# lsb_release -rd
Description: Ubuntu 14.04 LTS
Release: 14.04

2.)pkg-version
root@ubuntu-4crypt:/var/log# apt-cache policy cryptsetup
cryptsetup:
  Installiert: 2:1.6.1-1ubuntu1
  Installationskandidat: 2:1.6.1-1ubuntu1

3.)expected
root@ubuntu-4crypt:/var/log# zless /usr/share/doc/cryptsetup/README.initramfs.gz | grep timeout
The "key" part of /etc/crypttab will be interpreted as <device>:<path>[:<timeout>],
The timeout option has to be in seconds.

After timeout cryptsetup should ask for a passphrase to unlock the encrypted filesystem.

4.)unexpected
With my keyfile the system starts as expected; however the timeout option from the documentation has no effect at all...
Others already tried to report this, eg: https://answers.launchpad.net/ubuntu/+source/cryptsetup/+question/248155

5.)no logfiles
I can not provide logfiles, as I do not know how to log information about initramfs/upstart.
I have setup a vm to test this with lvm/sdaX_crypt.