XenialTestUefiLvmRootXfsBootXfs past fixby date but still failing

In https://jenkins.ubuntu.com/server/job/curtin-vmtest-devel-amd64/798/ we're seeing:

======================================================================
ERROR: test suite for <class 'vmtests.test_lvm_root.XenialTestUefiLvmRootXfsBootXfs'>
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/nose/plugins/multiprocess.py", line 788, in run
    self.setUp()
  File "/usr/lib/python3/dist-packages/nose/suite.py", line 293, in setUp
    self.setupContext(ancestor)
  File "/usr/lib/python3/dist-packages/nose/plugins/multiprocess.py", line 770, in setupContext
    super(NoSharedFixtureContextSuite, self).setupContext(context)
  File "/usr/lib/python3/dist-packages/nose/suite.py", line 316, in setupContext
    try_run(context, names)
  File "/usr/lib/python3/dist-packages/nose/util.py", line 471, in try_run
    return func()
  File "/var/lib/jenkins/slaves/torkoal/workspace/curtin-vmtest-devel-amd64/curtin-798/tests/vmtests/__init__.py", line 482, in wrapper
    raise RuntimeError(msg)
RuntimeError: skip_by_date(XenialTestUefiLvmRootXfsBootXfs.setUpClass) LP: #1652822 fixby=2019-06-01 removeby=2019-06-22: (PAST_FIXBY) Failed: Command '['tools/xkvm', '-v', '--dowait', '--uefi-nvram=/var/lib/jenkins/slaves/torkoal/workspace/curtin-vmtest-devel-amd64/output/XenialTestUefiLvmRootXfsBootXfs/disks/ovmf_vars.fd', '--netdev=user,mac=52:54:00:12:34:01', '--disk=/var/lib/jenkins/slaves/torkoal/workspace/curtin-vmtest-devel-amd64/output/XenialTestUefiLvmRootXfsBootXfs/disks/install_disk.img,driver=virtio-blk,format=raw,logical_block_size=512,physical_block_size=512,min_io_size=512,serial=4cd98c5c-7761-4179', '--disk=/var/lib/jenkins/slaves/torkoal/workspace/curtin-vmtest-devel-amd64/output/XenialTestUefiLvmRootXfsBootXfs/boot/output_disk.img,driver=virtio-blk,format=raw,logical_block_size=512,physical_block_size=512,min_io_size=512,serial=output_disk.img', '--disk=file=/var/lib/jenkins/slaves/torkoal/workspace/curtin-vmtest-devel-amd64/output/XenialTestUefiLvmRootXfsBootXfs/boot/seed.img,if=virtio,media=cdrom', '--', '-smp', '1', '-m', '1024', '-nographic', '-serial', 'file:/var/lib/jenkins/slaves/torkoal/workspace/curtin-vmtest-devel-amd64/output/XenialTestUefiLvmRootXfsBootXfs/logs/boot-serial.log']' timed out after 300 seconds

with the boot-serial.log file looking like this:

[=3h[=3h[=3h[=3h[=3h[=3h[=3herror: failure reading sector 0xb30 from `fd0'.

error: failure reading sector 0xa80 from `fd0'.

error: failure reading sector 0x0 from `fd0'.

error: failure reading sector 0xb30 from `fd1'.

error: failure reading sector 0xa80 from `fd1'.

error: failure reading sector 0x0 from `fd1'.

error: failure reading sector 0x0 from `cd0'.

error: failure reading sector 0xb30 from `fd0'.

error: failure reading sector 0xa80 from `fd0'.

error: failure reading sector 0x0 from `fd0'.

error: failure reading sector 0xb30 from `fd1'.

error: failure reading sector 0xa80 from `fd1'.

error: failure reading sector 0x0 from `fd1'.

error: failure reading sector 0x0 from `cd0'.

error: no such device: a45a16b8-018c-4a24-b9d8-aee19ca4566e.

GNU GRUB version 2.02~beta2-36ubuntu3.22

   Minimal BASH-like line editing is supported. For the first word, TAB

   lists possible command completions. Anywhere else TAB lists possible

   device or file completions.

grub>

We should dig in to why this hasn't ended up fixed as we expected.