trivial: Rework 'CreateServer' function

This rather complex function has had stuff tacked on over the years.
Help make working with it a bit easier through liberal application of
whitespace and some nicer indentation. Some option help text is improved
based on changes to modern nova.

Change-Id: I8154dd395dd904c3bcd180a7d0f9037b7e0be64f
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

Author: stephenfin