Switch to testrepository for running tests

OpenStack as a whole is moving towards using testrepository and
testtools for running tests. To that end, bring Glance into line by
switching it to use testrepository to run tests.

This copies run_tests.sh and tools/colorizer.py from Nova.

This change also has some minor changes to make run_test.sh work well.

Partial fixes bug: 1179009
Fixes bug: 1271806

Change-Id: Ic265bc0d2f1528358f6e8ee5b4139f991923fc72
Signed-off-by: Steve Kowalik <steven@wedontsleep.org>
Signed-off-by: Zhi Yan Liu <zhiyanl@cn.ibm.com>