Add stable/pike environment to tox for unit testing
Add stable/pike environment to tox for unit testing

Now neutron has cut stable/pike master is no longer the pike release so
we must add a unit test environment to track networking-cisco's
compatiblity with neutron stable/pike.

Change-Id: I7d9f584ea6376ba067051a6b311acecbe77325f3

Tehsmash/networking-cisco,noironetworks/networking-cisco,openstack/networking-cisco,noironetworks/networking-cisco,openstack/networking-cisco,Tehsmash/networking-cisco