make it possible to run only one test in tempest

we were always adding 'tempest' to the list for tests in
run_tests.sh, which didn't let you use the wrapper for running
a single tempest test. This change should fix that.

Probably could be cleaner, but my bash-fu is weaksause.

Change-Id: I5a3600b14214dd38be505481dad5ab72998df386
1 file changed