Add master tox env and allow all ostestr arguments
Add master tox env and allow all ostestr arguments

This patch adds a new tox entry point for testing against master
neutron, which can be used by doing tox -e master. This patch also
enables using all of the different ostestr arguments via tox by removing
the fixed --regex flag from tox.ini.

Change-Id: Icfc01ebf3a2dcec20c3c9efeff3de7ee320e84b0

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