pgsql: Stabilize query plans in rowsecurity regression test.

Stabilize query plans in rowsecurity regression test.

Some recent buildfarm failures can be explained by supposing that
autovacuum or autoanalyze fired on the tables created by this test,
resulting in plan changes. Do a proactive VACUUM ANALYZE on the
test's principal tables to try to forestall such changes.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/5cdf25e16843dff33dbc2ddc02941458032e3ad4

Modified Files
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src/test/regress/expected/rowsecurity.out | 41 +++++++++++++++--------------
src/test/regress/sql/rowsecurity.sql | 3 +++
2 files changed, 24 insertions(+), 20 deletions(-)