[eventlet-removal] Remove "logger" mechanism from ML2/OVN CI jobs

The "logger" mechanism is a testing class that is still calling
monkey_patch. This mechanism driver is not relevant nor neccessary
for the ML2/OVN CI jobs.

Change-Id: Ic8bbcd59ea06ad00255e9a5a640994e9e459a155

Author: ralonsoh

zuul.d/base.yaml

@@ -75,7 +75,10 @@
     vars:
       devstack_localrc:
         Q_AGENT: ovn
-        Q_ML2_PLUGIN_MECHANISM_DRIVERS: ovn,logger
+        # NOTE(ralonsoh): during the eventlet removal, the "logger" mech
+        # driver has been removed from this list. Re-add it once the removal
+        # is finished or the mech driver does not call monkey_patch().
+        Q_ML2_PLUGIN_MECHANISM_DRIVERS: ovn
         Q_ML2_PLUGIN_TYPE_DRIVERS: local,flat,vlan,geneve
         Q_ML2_TENANT_NETWORK_TYPE: geneve
         USE_PYTHON3: True