Remove underscore tests.init hack

This seems not needed anymore as tests pass without it, and it's not
Python 3 comptaible.

Change-Id: I93d161ea0b956b8e9560275453347a33dfeccf7c
Don't need to init testr in run_tests.sh

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 #1222688
Change-Id: I51e73efe4e9b80bbf0159a5bce0db81fc049b9ce
Merge "Remove underscore tests.init hack"
Merge "Don't need to init testr in run_tests.sh"