pgsql: Suppress attempts to report dropped tables to the stats collector

Log Message:
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Suppress attempts to report dropped tables to the stats collector from a
startup or recovery process. Since such a process isn't a real backend,
pgstat.c gets confused. This accounts for recent reports of strange
"invalid server process ID -1" log messages during crash recovery.
There isn't any point in attempting to make the report, since we'll discard
stats in such scenarios anyhow.

Tags:
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REL8_1_STABLE

Modified Files:
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pgsql/src/backend/storage/smgr:
smgr.c (r1.93.2.2 -> r1.93.2.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/smgr/smgr.c.diff?r1=1.93.2.2&r2=1.93.2.3)