pgsql: Fix installcheck for test_rls_hooks

Fix installcheck for test_rls_hooks

As pointed out by the buildfarm, test_rls_hooks wasn't functioning
properly with a clean installcheck. test_rls_hooks needs to explicitly
load the library with the hooks in it, to allow installcheck to work;
using the --temp-config doesn't help since that isn't used when running
installcheck and it isn't exactly fair to the buildfarm to modify the
installed config prior to calling installcheck.

Also, have test_rls_hooks clean up after itself.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/450fa1b5ba0e986a20d8c017500c0c0bbf1e0b4b

Modified Files
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src/test/modules/test_rls_hooks/expected/test_rls_hooks.out | 7 +++++++
src/test/modules/test_rls_hooks/sql/test_rls_hooks.sql | 11 +++++++++++
2 files changed, 18 insertions(+)