pgsql: Adjust Windows autovacuum service to retry for up to 5 minutes

Log Message:
-----------
Adjust Windows autovacuum service to retry for up to 5 minutes waiting
for the postmaster to start. Dave Page

Modified Files:
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pgsql/contrib/pg_autovacuum:
pg_autovacuum.c (r1.28 -> r1.29)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_autovacuum/pg_autovacuum.c.diff?r1=1.28&r2=1.29)