 Add missing py37 and corrected default envlist.
 Add missing py37 and corrected default envlist.

Change-Id: I408c179e66a58f80972727ad270126319d7ded0b

stackforge/python-openstacksdk,openstack/python-openstacksdk,openstack/python-openstacksdk,dtroyer/python-openstacksdk,stackforge/python-openstacksdk,dtroyer/python-openstacksdk