core: ConnectAllHostsToLun shouldn't run within transaction

The following command shouldn't run within transaction, it performs vdsm
operations only and no db updates -  Running it within transaction can
cause to timeout and leave unneeded connections.

Change-Id: I6d3bcbc8a61102439fdf732f7c969b1baf8ad8bf
Signed-off-by: Liron Aravot <laravot@redhat.com>