Check for image_meta in libvirt.driver.spawn

This adds check that image_meta exists in libvirt driver
spawn method. In case it doesn't the image shouldn't be
created.

part of libvirt driver support for blueprint rebuild-for-ha

DocImpact

Change-Id: I097c7cbfde96bcb21b4f06af4e5bac00440849c2
Co-authored-by: Oshrit Feder <oshritf@il.ibm.com>
Merge "Check for image_meta in libvirt.driver.spawn"