Fix the gabbi target in tox.ini to use correct path
Fix the gabbi target in tox.ini to use correct path

This was never updated when the functional tests were moved. This is
just a convenience target so the problem was never noticed.

Change-Id: Icce30d3de430b1302993a24a0e2b790f6906128c

openstack/aodh,openstack/aodh