With this patch, nova will automatically quiesce active volume boot
instances on creating volume snapshots by image-create command.
After volume snapshots are completed, the instance is unquiesced.
if the boot volume has 'os_require_quiesce=yes' image metadata,
the snapshotting is aborted when quiescing fails. Otherwise,
quiescing is skipped and the snapshotting is continued.
To utilize this feature in KVM instances, qemu-guest-agent must be
installed in the guest and the image metadata must have
'hw_qemu_guest_agent=yes' property.
Change-Id: Ic43dfa441fad8fefaa41b1db43ad19b15dc483c3
Implements: blueprint quiesced-image-snapshots-with-qemu-guest-agent
d04b8a3a21