libvirt: ignore NOSTATE in resume_state_on_host_boot() method.

Occasionally, libvirt would get NOSTATE from hypervisor as instance
state. Thus if we don't ignore instances in NOSTATE in
resume_state_on_host_boot() method, we would mistakenly reboot such
instances when we restart nova-compute service or on host boot. This
patch fixes this by adding NOSTATE into ignored_states.

Bug 1176897

Change-Id: I651cb043d7f97fde29b2a62e6ead8222062f01f7
Merge "libvirt: ignore NOSTATE in resume_state_on_host_boot() method."