Remove a py34 environment from tox
Remove a py34 environment from tox

The gating on python 3.4 is restricted to <= Mitaka. This is due to
the change from Ubuntu Trusty to Xenial, where only python3.5 is
available. There is no need to continue to keep these settings.

Change-Id: Id8a9dda9ea25b47afc35e0605f4df2f3f22c5f38

vponomaryov/manila,vponomaryov/manila,bswartz/manila,bswartz/manila,openstack/manila,openstack/manila