Updating L3 plugin to accomodate upstream changes

Some of router functions (i.e. update, delete, etc) have been updated
to invoke ML2 fuctions which are executed in the session's context.
Arista L3 Plugin was invoking router base class funtions in context
as well. This now causes the problem because of upstream changes.
This patch removes those calls from the session's context.

Change-Id: Ifa859f3076f73528b36c6395001ff4b9f6958bce

networking_arista/l3Plugin/l3_arista.py

@@ -103,10 +103,9 @@ class AristaL3ServicePlugin(db_base_plugin_v2.NeutronDbPluginV2,
         tenant_id = router['router']['tenant_id']
 
         # Add router to the DB
-        with context.session.begin(subtransactions=True):
-            new_router = super(AristaL3ServicePlugin, self).create_router(
-                context,
-                router)
+        new_router = super(AristaL3ServicePlugin, self).create_router(
+            context,
+            router)
         # create router on the Arista Hw
         try:
             self.driver.create_router(context, tenant_id, new_router)
@@ -122,13 +121,12 @@ class AristaL3ServicePlugin(db_base_plugin_v2.NeutronDbPluginV2,
     def update_router(self, context, router_id, router):
         """Update an existing router in DB, and update it in Arista HW."""
 
-        with context.session.begin(subtransactions=True):
-            # Read existing router record from DB
-            original_router = super(AristaL3ServicePlugin, self).get_router(
-                context, router_id)
-            # Update router DB
-            new_router = super(AristaL3ServicePlugin, self).update_router(
-                context, router_id, router)
+        # Read existing router record from DB
+        original_router = super(AristaL3ServicePlugin, self).get_router(
+            context, router_id)
+        # Update router DB
+        new_router = super(AristaL3ServicePlugin, self).update_router(
+            context, router_id, router)
 
         # Modify router on the Arista Hw
         try:
@@ -155,9 +153,7 @@ class AristaL3ServicePlugin(db_base_plugin_v2.NeutronDbPluginV2,
                           "router %(r)s exception=%(e)s"),
                       {'r': router, 'e': e})
 
-        with context.session.begin(subtransactions=True):
-            super(AristaL3ServicePlugin, self).delete_router(context,
-                                                             router_id)
+        super(AristaL3ServicePlugin, self).delete_router(context, router_id)
 
     @log_helpers.log_method_call
     def add_router_interface(self, context, router_id, interface_info):