s390x/kvm: Guest Migration TOD clock synchronization

Synchronizes the guest TOD clock across a migration by sending the guest TOD
clock value to the destination system. If the guest TOD clock is not preserved
across a migration then the guest's view of time will snap backwards if the
destination host clock is behind the source host clock. This will cause the
guest to hang immediately upon resuming on the destination system.

Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>

Message-Id: <1425912968-54387-1-git-send-email-jfrei@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>