Summary:
These tests expect DDLs like DROP/TRUNCATE to abort in progress DMLs and make progress. This doesn't hold true with object locking enabled. Hence, disabled object locking for the tests.
Jira: DB-17807

Test Plan: ./yb_build.sh --cxx-test pg_tablet_shutdown-test --gtest_filter *PgTabletShutdownTest*

Reviewers: rthallam, yyan, amitanand

Reviewed By: yyan

Subscribers: ybase, yql

Differential Revision: https://phorge.dev.yugabyte.com/D45803