Add full-stack test

Add full-stack test

Currently, the full-stack framework has only one test which only uses
the neutron-server. This patch adds an actual test which makes sure that
once a router is created, an actual namespace is create for it. Since
this test requires 3 processes (neutron-server, l3-agent, ovs-agent),
existing full-stack code is modified to add more streamlined support for
such code.

Partially-Implements: blueprint integration-tests
Change-Id: Id5a8852d38543590b90e4bbed261a7a458071a9a