Xenial deployments fail after updating boot-source to ‘daily’ instead of ‘releases’

[Tytus Kurek]

=== Description ===

After updating boot-source to point to the following URL:

http://maas.ubuntu.com/images/ephemeral-v2/daily/

when deploying with Ubuntu Trusty and "hwe-x" kernel nodes fail to deploy with errors displayed on the console as shown on attached screenshots (screenshots.tar.gz). No custom curtin configs are being passed.

=== Additional information ===

1. Contents of /var/log/maas/*:

Attached (logs.tar.gz)

2. Output from dpkg -l '*maas*'|cat

root@os-maas-1:~# dpkg -l '*maas*'|cat
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==================================-===================================-============-===============================================================================
ii maas 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS server all-in-one metapackage
ii maas-cli 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS command line API tool
ii maas-cluster-controller 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS server cluster controller
ii maas-common 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS server common files
ii maas-dhcp 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS DHCP server
ii maas-dns 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS DNS server
ii maas-proxy 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS Caching Proxy
ii maas-region-controller 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS server complete region controller
ii maas-region-controller-min 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS Server minimum region controller
ii python-django-maas 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS server Django web framework
ii python-maas-client 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS python API client
ii python-maas-provisioningserver 1.9.4+bzr4592-0ubuntu1~trusty1 all MAAS server provisioning libraries

3. Instructions on how we can re-create your bug and what the expected result should be.

* Install MaaS according to the version provided above
* Update default boot-source according to the following command:

maas maas-root boot-source update 1 url="http://maas.ubuntu.com/images/ephemeral-v2/daily/"

* Attempt to deploy a node with Ubuntu Trusty and "hwe-x" kernel