Add the functional-py34 and dsvm-functional-py34 targets to tox.ini
Add the functional-py34 and dsvm-functional-py34 targets to tox.ini

This will allow us to run the functional tests on the gates using Python 3.

Change-Id: I218c73398c6ed6cff776b65a66cb9336219cba77
Partial-Bug: #1500400

bigswitch/neutron,openstack/neutron,cloudbase/neutron,jumpojoy/neutron,sebrandon1/neutron,wolverineav/neutron,igor-toga/local-snat,chitr/neutron,jumpojoy/neutron,sebrandon1/neutron,huntxu/neutron,asgard-lab/neutron,bigswitch/neutron,mahak/neutron,chitr/neutron,klmitch/neutron,dims/neutron,noironetworks/neutron,mahak/neutron,glove747/liberty-neutron,huntxu/neutron,openstack/neutron,apporc/neutron,asgard-lab/neutron,apporc/neutron,eayunstack/neutron,openstack/neutron,yanheven/neutron,yanheven/neutron,mahak/neutron,MaximNevrov/neutron,igor-toga/local-snat,glove747/liberty-neutron,klmitch/neutron,cloudbase/neutron,dims/neutron,noironetworks/neutron,MaximNevrov/neutron,wolverineav/neutron,eayunstack/neutron