InvalidCPUInfo exception added to except block

When a live migration between two nodes with different
CPU info features is launched, an InvalidCPUInfo exception
is raised and not captured. That lets the vm in an
unusable state because the task_state rollback is not
executed.

Change-Id: Ib418fa324964cabd5f342d1b764f9ac7608b7ade
Closes-Bug: #1294210
(cherry picked from commit 7a3b4033f07f8c2144a36c1f12b1b9281cfb9a69)
Catch InstanceNotFound exception if migration fails

When a VM with an attached iSCSI disk fails to migrate, the rollback methods
does not detach the disk from target host. What happens is _lookup_by_name()
fails, since the VM does not exist on the target host. In detach_volume(), it
is supposed to print a warning based on the correct error code being returned,
instead of throwing the exception. However, this is not happening, because
_lookup_by_name() throws an InstanceNotFound exception, rather than a
libvirt.libvirtError exception. So we also need to catch InstanceNotFound
exception, so that detach_volume() can continue to execute as expected.

Change-Id: I396c23d8137bf1e2834769c5483d2494506949ad
Closes-Bug: #1321082
(cherry picked from commit 52b57e82c7ef972508777a8bd3c7b937a3673d2d)
Merge "InvalidCPUInfo exception added to except block" into stable/icehouse
Merge "Catch InstanceNotFound exception if migration fails" into stable/icehouse