nova.py: Remove docs for unused config settings

AFAICT, these settings are not used. I wonder if @mavimo meant to implement these later, but never got around to it? I'm not the only one who noticed this and was confused by it (see https://github.com/ansible/ansible/pull/7444#issuecomment-43503710).

The other way to go is to implement these settings, but I'm not familiar with these, don't think that my company needs them, and I'm not sure if they require a newer version of python-novaclient or something. In short, I don't feel qualified to implement support, so I'm just removing the docs for the unimplemented feature. Someone else that needs these settings could perhaps add them in at a later date.

BTW, one of settings, `insecure` was misspelled as `insicure` (sic).

Cc: @mavimo, @carsongee (because if this gets merged, #7444 will probably need to be rebased, because it probably touches a lot of the same lines.