remove workarounds in devstackgaterc
remove workarounds in devstackgaterc

1. remove workaround: remove non-exist q-odl
2. minior cleanup: change mysql from db type to service

Change-Id: I1ae5e2d6e945d9551ec244c550d1dcc6b6ee7d4d
related-Bug: #1633242

openstack/networking-odl,openstack/networking-odl,openstack/networking-odl