Adds new typed param for migration and uses this as a UNIX socket path that should be used for the NBD part of migration. And also adds virsh support. Partially resolves: https://bugzilla.redhat.com/1638889 Signed-off-by: Martin Kletzander <mkletzan@redhat.com> Reviewed-by: Jiri Denemark <jdenemar@redhat.com>