[FT] Add a timeout for the NB/SB connection stop method

If the DB connection is not stopped at the defined timeout (10 seconds),
the clean-up process will continue.

Closes-Bug: #2034589
Change-Id: I6c3b4da49364c3fed86053515e79121acac078d6
(cherry picked from commit b40c728)

Author: ralonsoh

neutron/tests/functional/base.py

@@ -407,8 +407,12 @@ def stop(self):
         if self.maintenance_worker:
             self.mech_driver.nb_synchronizer.stop()
             self.mech_driver.sb_synchronizer.stop()
-        self.mech_driver.nb_ovn.ovsdb_connection.stop()
-        self.mech_driver.sb_ovn.ovsdb_connection.stop()
+        for ovn_conn in (self.mech_driver.nb_ovn.ovsdb_connection,
+                         self.mech_driver.sb_ovn.ovsdb_connection):
+            try:
+                ovn_conn.stop(timeout=10)
+            except Exception:  # pylint:disable=bare-except
+                pass
 
     def restart(self):
         self.stop()