pgsql: Make GIN regression test stable.

Make GIN regression test stable.

Commit 7f46eaf added the regression test which checks that
gin_clean_pending_list() cleans up the GIN pending list and returns >0.
This usually works fine. But if autovacuum comes along and cleans
the list before gin_clean_pending_list() starts, the function may
return 0, and then the regression test may fail.

To fix the problem, this commit disables autovacuum on the target
index of gin_clean_pending_list() by setting autovacuum_enabled
reloption to off when creating the table.

Also this commit sets gin_pending_list_limit reloption to 4MB on
the target index. Otherwise when running "make installcheck" with
small gin_pending_list_limit GUC, insertions of data may trigger
the cleanup of pending list before gin_clean_pending_list() starts
and the function may return 0. This could cause the regression test
to fail.

Per buildfarm member spoonbill.

Reported-By: Tom Lane

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/f8a1c1d5a30003c9c24b00870d5a0f02f1c81e65

Modified Files
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src/test/regress/expected/gin.out | 5 +++--
src/test/regress/sql/gin.sql      | 5 +++--
2 files changed, 6 insertions(+), 4 deletions(-)