libxl: migration: defer removing VM until finish phase

libxl: migration: defer removing VM until finish phase

If for any reason the restore of a VM fails on the destination host
in a migration operation, the VM is removed (if not persistent) from
the virDomainObjList, meaning it is no longer available for additional
cleanup or processing in the finish phase. Defer removing the VM from
the virDomainObjList until the finish phase, which already contains
logic to remove the VM.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
ACKed-by: Michal Privoznik <mprivozn@redhat.com>