Remove use of unsupported TEMPEST_SERVICES variable
Remove use of unsupported TEMPEST_SERVICES variable

TEMPEST_SERVICES global variable is not supported
by devstack since long back.
- I380dd20e5ed716a0bdf92aa02c3730359b8136e4
- I9c24705e494689f09a885eb0a640efd50db33fcf

Service availability of tempest known services will be
set by devstack with local check.
- I02be777bf93143d946ccbb8e9eff637bfd1928d4

cloudkitty does not have tempest plugin so it does
not need to have service register in tempest.

This commit removes the TEMPEST_SERVICES setting.

Change-Id: Ica3d142ad1c95379771fc1f045dd7e80ca0452a5
Related-Bug: #1743688

openstack/cloudkitty,stackforge/cloudkitty,stackforge/cloudkitty,openstack/cloudkitty