commands: after adding the node to the DB we need to commit

rocks add host vm needed an extra commit to the DB before it could
preceed.

Oddly this problem was showing only with using real DNS name for
the FE (I didn't really understand why this).

So if the physical frontend is a somename.ucsd.edu and you try to
run:
rocks add host vm localhost Frontend sync-config=n name=mail
(and mail.ucsd.edu exists) it will fail without this patch