Add tunneling support to full stack tests

Add tunneling support to full stack tests

* EnvironmentDescription class now accepts 'network_type'.
  It sets the ML2 segmentation type, passes it to the OVS agents
  configuration files, and sets up the host configuration. If
  tunnelling type is selected, it sets up a veth pair with an IP
  address from the 240.0.0.1+ range. The addressed end of
  this pair is configured as the local_ip for tunneling purposes
  in each of the OVS agents. If network type is not tunnelled, it
  sets up provider bridges instead and interconnects them.
* For now we run the basic L3 HA test with VLANs and tunneling just
  so we have something to show for.
* I started using scenarios in fullstack tests to run the same test
  with VLANs or tunneling, and because test names are used for log
  dirs, and testscenarios changes test names to include characters
  that are not shell friendly (Space, parenthesis), I 'sanitized'
  some of those characters.

Change-Id: Ic45cc27396452111678cf85ab26b07275846ce44