Delete the lb configuration files during cleanup

The issue is seen because boost::filesystem::remove
is used to delete the lb pool configuration directory.
Since the directory is not empty, it is failing.

This patch fixes the issue by calling
boost::filesystem::remove_all instead of delete
the files if the directory is not empty.

Change-Id: I48ced8fc1ef86063127ff50d42a40592082d27cb
Closes-bug: #1399241

src/vnsw/agent/oper/instance_manager.cc

@@ -671,7 +671,7 @@ void InstanceManager::LoadbalancerObserver(
             haproxy_->GenerateConfig(pathgen.str(), loadbalancer->uuid(),
                                      *loadbalancer->properties());
         } else {
-             boost::filesystem::remove(pathgen.str(), error);
+             boost::filesystem::remove_all(pathgen.str(), error);
              if (error) {
                  LOG(ERROR, error.message());
                  return;