Remove duplicated log related to slot creation in pg_createsubscriber

Remove duplicated log related to slot creation in pg_createsubscriber

The creation of a replication slot done in a specific database on a
publisher was logged twice, with the second log not mentioning the
database where the slot creation happened.  This commit removes the
information logged after a slot has been successfully created, moving
the information about the publisher from the second to the first log.
Note that failing a slot creation is also logged, so there is no loss of
information.

Author: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CAHut+Pv7qDvLbDgc9PQGhULT3rPXTxdu_=w+iW-kMs+zPADR+w@mail.gmail.com