pgsql: Fix incorrect initialization of BackendActivityBuffer.

Fix incorrect initialization of BackendActivityBuffer.

Since commit c8e8b5a6e, this has been zeroed out using the wrong length.
In practice the length would always be too small, leading to not zeroing
the whole buffer rather than clobbering additional memory; and that's
pretty harmless, both because shmem would likely start out as zeroes
and because we'd reinitialize any given entry before use.  Still,
it's bogus, so fix it.

Reported by Petru-Florin Mihancea (bug #15312)

Discussion: https://postgr.es/m/153363913073.1303.6518849192351268091@wrigleys.postgresql.org

Branch
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REL9_4_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/753051cc721e9123e817b929b257e53a9b97a502

Modified Files
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src/backend/postmaster/pgstat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)