Remove global DB_ENGINE from Neutron

Related-Bug 1207402

This global is not used anymore as it's been replaced by a similar
global variable in neutron/openstack/common/db/sqlalchemy/session.py

Change-Id: Id4614069af490020d18f14011853787930076e0a

neutron/db/api.py

@@ -25,7 +25,6 @@ from neutron.openstack.common import log as logging
 
 LOG = logging.getLogger(__name__)
 
-_DB_ENGINE = None
 BASE = model_base.BASEV2
 
 
@@ -35,17 +34,13 @@ def configure_db():
     Establish the database, create an engine if needed, and register
     the models.
     """
-    global _DB_ENGINE
-    if not _DB_ENGINE:
-        _DB_ENGINE = session.get_engine(sqlite_fk=True)
-        register_models()
+    session.get_engine(sqlite_fk=True)
+    register_models()
 
 
 def clear_db(base=BASE):
-    global _DB_ENGINE
     unregister_models(base)
     session.cleanup()
-    _DB_ENGINE = None
 
 
 def get_session(autocommit=True, expire_on_commit=False):

neutron/plugins/metaplugin/meta_neutron_plugin.py

@@ -73,8 +73,6 @@ class MetaPluginV2(db_base_plugin_v2.NeutronDbPluginV2,
                        in cfg.CONF.META.plugin_list.split(',')]
         for flavor, plugin_provider in plugin_list:
             self.plugins[flavor] = self._load_plugin(plugin_provider)
-            # Needed to clear _DB_ENGINE for each plugin
-            db._DB_ENGINE = None
 
         self.l3_plugins = {}
         l3_plugin_list = [plugin_set.split(':')
@@ -86,7 +84,6 @@ class MetaPluginV2(db_base_plugin_v2.NeutronDbPluginV2,
             else:
                 # For l3 only plugin
                 self.l3_plugins[flavor] = self._load_plugin(plugin_provider)
-                db._DB_ENGINE = None
 
         self.default_flavor = cfg.CONF.META.default_flavor
         if self.default_flavor not in self.plugins: