OVSDB fix exporting routes for existing VRF

Issue:
------
if client comes after vrf is available it fails to export route
table till further change happens on vrf entry.

Fix:
----
start walk on vrf table in VrfOvsdbObject Constructor to iterate
through existing VRF entries and export them

Change-Id: I392395a719ceeb8381fa46f478cf74f7d7560492
Closes-Bug: 1420130

src/vnsw/agent/ovs_tor_agent/ovsdb_client/unicast_mac_remote_ovsdb.cc

@@ -311,6 +311,13 @@ VrfOvsdbObject::VrfOvsdbObject(OvsdbClientIdl *idl, DBTable *table) :
     walkid_(DBTableWalker::kInvalidWalkerId) {
     vrf_listener_id_ = table->Register(boost::bind(&VrfOvsdbObject::VrfNotify,
                 this, _1, _2));
+
+    // Trigger Walk to get existing vrf entries.
+    DBTableWalker *walker = idl->agent()->db()->GetWalker();
+    walkid_ = walker->WalkTable(table_, NULL,
+            boost::bind(&VrfOvsdbObject::VrfWalkNotify, this, _1, _2),
+            boost::bind(&VrfOvsdbObject::VrfWalkDone, this, _1));
+
     client_idl_->Register(OvsdbClientIdl::OVSDB_UCAST_MAC_REMOTE,
             boost::bind(&VrfOvsdbObject::OvsdbRouteNotify, this, _1, _2));
 }