Install networking support on a dedicated compute node.

rpc_backend is changed for all distributions.

Change-Id: I46b71c9f76e56cde57c7916dae433391076d63bb
backport: havana
Closes-Bug: #1246840
Install Guide: make sure that the admin can use the nova command

The first nova command example might be executed on a compute node by
the user, and it's likely that python-novaclient has not been installed
there. Suggest to the user to log on the controller or to install the
client.

Change-Id: I57009deb4a817966f9a37036f3230a418a5133e3
Partial-Bug: #1245946
backport: havana
Merge "Install networking support on a dedicated compute node."
Merge "Install Guide: make sure that the admin can use the nova command"