postgres_fdw: Third attempt to stabilize regression tests.

postgres_fdw: Third attempt to stabilize regression tests.

Commit 1bc0100d270e5bcc980a0629b8726a32a497e788 added this test,
and commit 882ea509fe7a4711fe25463427a33262b873dfa1 tried to
stabilize it.  There were still failures, so commit
958e20e42d6c346ab89f6c72e4262230161d1663 tried again to stabilize
it.  That approach is still failing on jaguarundi, though, so
back it out and try something else.  Specifically, instead of
disabling remote estimates for the table in question, let's tell
autovacuum to leave it alone.

Etsuro Fujita

Discussion: http://postgr.es/m/5A82DCCE.3060107@lab.ntt.co.jp