Delete router routes before router delete in unittest teardown

Closes bug: #1556882

Change-Id: I1d777a774e80650cbb137b4e083a5fcc299a01e8

networking_cisco/tests/unit/cisco/l3/test_db_routertype.py

@@ -195,6 +195,10 @@ class RoutertypeTestCaseMixin(object):
             for r in routers:
                 if r['id'] in auto_deleted_router_ids:
                     continue
+                # Remove any static routes
+                if r.get('routes'):
+                    self._update('routers', r['id'],
+                                 {'router': {'routes': None}})
                 # Remove any floatingips using the router
                 for fip in self._list(
                         'floatingips',