Fix tempest tests list
Fix tempest tests list

Running command `testr list-tests zaqar` under tempest directory
get an empty list instead of the list of zaqar tempest list. This
patch set bath_path to the top directory of zaqar.

Change-Id: I8c91b83bfb5da37a95d6a797f1882221ccdc437a
Closes-Bug: #1563925

openstack/zaqar,openstack/zaqar,openstack/zaqar,openstack/zaqar