Put py34 first in the env order of tox and remove py33
Put py34 first in the env order of tox and remove py33

To solve the problem of "db type could
not be determined" on py34 we have to run first the py34 env to, then,
run py27. This patch puts py34 first on the tox.ini list of envs to
avoid this problem to happen. Also as py33 is not supported from Mitaka,
this patch removes the support for the same from tox.ini

Change-Id: I5f7172465f2f0531a41babe78d917ec6fa32c7a8
Closes-bug: #1489059

stackforge/networking-mlnx,openstack/networking-mlnx,stackforge/networking-mlnx,openstack/networking-mlnx