All tests should be included in testr.

In test_common.py, the testr command line will be read for parsing,
finally emit error message:
run.py: error: no such option: -t

we should mock the sys.argv in setUp().

The analysis is here
--------------------
troveclient/compat/common.py: CommandsBase
254     def _parse_options(self, parser):
255         opts, args = parser.parse_args()  <-- 1. no arg is passed

/usr/lib/python2.7/optparse.py
1361     def _get_args(self, args):
1362         if args is None:
1363             return sys.argv[1:]  <-- 3. cmdline(testr command) is read
1364         else:
1365             return args[:]

1367     def parse_args(self, args=None, values=None):
...
1381         rargs = self._get_args(args) <-- 2. args is None

Close-Bug #1241845

Change-Id: I092db96d1b6bb31c41e6ba4c5fc9606e3f8ac087