Fix PostReceive reftx hook test
While TestPostReceiveWithReferenceTransactionHook succeeds when run as part of the smarthttp testsuite, it fails when run standalone. The issue is that the test didn't set up the hooks override and thus hooks cannot be located correctly in case the test is run standalone. In case it's run as part of the smarthttp suite, it succeeds because previous tests failed to correctly restore the old value.
Fix the test by correctly setting up hooks.Override
and correctly
restoring its value after the tests.