libvirt: Use VIR_DOMAIN_AFFECT_LIVE for paused instances

When a volume is attached to a paused instance, it does not
appear in the instance's block devices list (i.e. lsblk)
after the instance has resumed. A similar situation
happens when detaching a volume from a paused instance; the
block device continues to exists in the block devices list,
where it should not.  It was found that the volume is only
persisted in the domain's config settings and not its active
settings, since only the VIR_DOMAIN_AFFECT_CONFIG flag was used
on attach and detach volume.  In order to affect the active
settings, the VIR_DOMAIN_AFFECT_LIVE flag has to be added when
attaching and detaching volumes.

This change adjusts little about the unit test:
add two imports.

Change-Id: I9c90a410a7ecb91f5a4de28acee21fe7da49242c
Closes-Bug: #1242366
Related-Bug: #1299331
(cherry picked from commit ead9cfca93c9b5ca55e3ba269213c98d5e6e1d38)
Merge "libvirt: Use VIR_DOMAIN_AFFECT_LIVE for paused instances" into stable/icehouse