Nova.conf and Metadata-agent file consistency updates

This PR resolves https://github.com/rcbops/ansible-lxc-rpc/issues/79 while
also cleaning up the nova.conf template file as well as the metadata-agent.ini file.

removed unused variables

commented everything and added port / caching as explicite settings

removed whitespace

File clean up

Commeneted everything as sections in the file. Added +metadata_host and +metadata_port.
Nothing else was added or removed however the contents were moved around in the file to
make it more consistent and legible.