TrivialFix: '_lport_index' is used prior to global declaration
TrivialFix: '_lport_index' is used prior to global declaration

Fix warning: dragonflow/tests/unit/test_app_base.py:216: SyntaxWarning: name
'_lport_index' is used prior to global declaration

Change-Id: Ifba4ccf6fcc2dcfb2e6b5fe505fc1a0be48f7ce6

openstack/dragonflow,openstack/dragonflow,openstack/dragonflow