doc: Consolidate NetRestrict format docmentation

doc: Consolidate NetRestrict format docmentation

We were specifying exactly the same format in two different places;
consolidate them into one place. In addition, explicitly say there are
is no way to specify a range of addresses, in case some people are
confused by the previous versions of this man page that erroneously
said you could use 255 as a wildcard.

Reviewed-on: http://gerrit.openafs.org/7565
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit d4bab02f023f53041c3ac58fd75cffd27ec92df0)

Change-Id: I7bae4786b6a0cc2115688bd54d1c1128dc0f5df2
Reviewed-on: http://gerrit.openafs.org/7671
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>