Add fullstack testing doc content
Add fullstack testing doc content

* Tighten the opening paragraph
* Explain RabbitMQ 'vhosts'
* Add an example

Change-Id: Ic905afb3b5fa8674647413a8df67b5ddcadfd75f

igor-toga/local-snat,mahak/neutron,bigswitch/neutron,openstack/neutron,bigswitch/neutron,wolverineav/neutron,cloudbase/neutron,klmitch/neutron,openstack/neutron,sebrandon1/neutron,huntxu/neutron,sebrandon1/neutron,eayunstack/neutron,openstack/neutron,apporc/neutron,wolverineav/neutron,klmitch/neutron,mahak/neutron,noironetworks/neutron,dims/neutron,MaximNevrov/neutron,chitr/neutron,cloudbase/neutron,mahak/neutron,noironetworks/neutron,chitr/neutron,dims/neutron,huntxu/neutron,igor-toga/local-snat,MaximNevrov/neutron,apporc/neutron,eayunstack/neutron