Add 'rm -f .testrepository/times.dbm' command in testenv
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.
Closes-Bug: #1565928

Change-Id: I9166e375fe3c3e223fb91f4e09d7ed903689cbc2

openstack/dragonflow,openstack/dragonflow,openstack/dragonflow