[WIP]: neutron: configure contrail backend for control and compute nodes.

[mmnelemane]

These changes to the neutron barclamp is done to enable configuring Contrail backend for neutron. The following points summarizes the actions done:

• Allows setting of "networking_plugin" type to "contrail"
• Installs Contrail packages on control and compute nodes
• Configures neutron to use Contrail as the SDN backend (non-ML2)
• Configures ContrailPlugin.ini with parameters to access the contrail-server.
• It assumes that the Contrail control plane server is already up and running in the admin-network. Configuration of this node is not part of the barclamp.
• The packages installed are currently from a private repository and hence require ignoring gpg-keys which is not supported by the standard "package" syntax of chef. Hence the script uses direct "zypper --no-gpg-checks" command to setup the packages.
• The compute node is configured and populated with a script "set_vhost_interfaces.sh" in the /root/ folder that needs to be run from the serial console since running it on ssh will disconnect the node.

Note: The PR is created to check if the changes do not break the normal operations so that it can be used for POCs. Considerable work is required to be done for the packages as well as the barclamp to get this ready for review.

[toabctl]

@mmnelemane do you plan to continue on this soon?