libvirt: Catch VIR_ERR_NO_DOMAIN in list_instances

Commit 25f50d9a didn't catch the exact exception for
looking up deleted domain.

Partly fixes LP Bug #1032741.

Change-Id: I6c6f7d8a736c833488b6cb8e00530dc4138f1424
Merge "libvirt: Catch VIR_ERR_NO_DOMAIN in list_instances"