pgsql: Avoid useless snprintf() call when update_process_title is turned

Log Message:
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Avoid useless snprintf() call when update_process_title is turned off.
Fujii Masao

Modified Files:
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pgsql/src/backend/replication:
walreceiver.c (r1.11 -> r1.12)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/replication/walreceiver.c?r1=1.11&r2=1.12)