Add 'rm -f .testrepository/times.dbm' command in testenv

Running py2* post py3* tests results in error. Add
'rm -f .testrepository/times.dbm' command in testenv to
resolve this.

Change-Id: Ide2e6f2fe9d5b3c7b33e2fefdd3d306284684ba1

tox.ini

@@ -16,9 +16,10 @@ setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands =
+  rm -f .testrepository/times.dbm
   python tools/patch_tox_venv.py
   python setup.py testr --slowest --testr-args='{posargs}'
-
+ 
 [tox:jenkins]
 sitepackages = False