Don't need to init testr explicitly

In run_tests.sh, function init_testr will initialize testr if the
directory .testrepository is not existed. Actually, testr will do
the check before run the test:

In Python package testrepository, setuptools_command.py:Testr.run

68 def run(self):
69 """Set up testr repo, then run testr"""
70     if not os.path.isdir(".testrepository"):
71     self._run_testr("init")

So, init_testr can be removed safely.

Fixes Bug #1220147

Change-Id: Ide99a836cd601453624c7a562b7256c86bd46811