Added "novncproxy_base_url" directive to nova.conf

Added "novncproxy_base_url" directive to nova.conf for RHEL and SUSE.
Also unified formatting/phrasing around this directive and other
directives in this step for all distributions.  Without this
directive, URLs for remote console access to instances reference
localhost (127.0.0.1) rather than the controller node.

Change-Id: Id4e8c09c7bc81a2314bd9fea80e48349f19fb224
Closes-Bug: #1258287