[FT] Clear the idl lock in TestMaintenance tests

One or the other test in TestMaintenance fails
randomly with missing idl lock.

DBInconsistenciesPeriodics set's the idl lock
but in TestMaintenance we don't run it as a seperate
maintenance worker and instead call check_for_inconsistencies
when needed so not a requirement to have a dedicated lock.
This patch clears the lock for these tests to avoid
such random issues.

Closes-Bug: #2039417
Change-Id: I931997fe010295120f2400b1ec310dff82497ab6
(cherry picked from commit 39a1f1e)

Author: karelyatin

neutron/tests/functional/plugins/ml2/drivers/ovn/mech_driver/ovsdb/test_maintenance.py

@@ -50,6 +50,8 @@ def setUp(self):
         ext_mgr = test_extraroute.ExtraRouteTestExtensionManager()
         self.ext_api = test_extensions.setup_extensions_middleware(ext_mgr)
         self.maint = maintenance.DBInconsistenciesPeriodics(self._ovn_client)
+        # Release the unneeded lock
+        self.maint._idl.set_lock(None)
         self.context = n_context.get_admin_context()
         # Always verify inconsistencies for all objects.
         db_rev.INCONSISTENCIES_OLDER_THAN = -1