Don't explode if we fail to unplug VIFs after a failed boot

Libvirt currently attempts to unplug VIFs after destroying an
instance, which can fail if the instance was never built
properly in the first place. This patch makes it ignore errors
when trying to tear down VIFs during that cleanup. Failure
in this case would block the deletion of the instance (which
should never happen) and any real failures aren't something
we could do anything about.

Closes-bug: #1306718

Change-Id: I84a4433c3959b8f14e0259be0aa51da1654006c8
(cherry picked from commit b3225581befe14f21b909e176d0a4583b297e031)
Fix display of server group members

The previous code was failing to display the members of server
groups because it was filtering them all out.

Interestingly, the previous code passes the unit tests due to a
bug where we treat regex comparisons differently when using mysql
vs sqlite (tracked under bug 1298690).

Change-Id: I7be9c180f4284dd18cd02e510e77e3c1e3fc9925
Closes-bug: 1298494
(cherry picked from commit 8ce30b6ac7ea8d2e036a621a9904b35cb1563672)
Merge "Fix display of server group members" into stable/icehouse