Add run_test.sh for running tests

This is a copy of the test entry point used in Nova, Swift, Keystone,
Tuskar, Glance, Horizon, Neutron, Heat, Cinder, and others. It
provides a simple way to add consistency and repeatability to running
tests w/ minimal human effort, just run ./run_tests.sh.

Change-Id: I7d9369f7c86b62a6e7ba9b66344d6ad25596251f
Merge "Add run_test.sh for running tests"