grizzly: changes to fixed_range option need documentation

[Tom Fifield]

https://review.openstack.org/#/c/23787/ has a feature freeze exception, to bring some sanity to nova's fixed_range option:

DocImpact: For backwards compatibility, Grizzly will still support
the CONF.fixed_range option and if set will perform the default logic
from Folsom and earlier releases. The intention is to remove the
CONF.fixed_range option early in the Havana cycle.

   109 # TODO(mathrock): Deprecate in Grizzly, remove in Havana
 109 cfg.StrOpt('fixed_range', 110 cfg.StrOpt('fixed_range',
 110 default='10.0.0.0/8', 111 default=None,
 111 help='Fixed IP address block'), 112 help='DEPRECATED - Fixed IP address block.'
   113 'If not set, default to automatically determining the '
   114 'fixed_range by pulling from the configured networks'),

This is important to document due to operations impact.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/24717

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/24717
Committed: http://github.com/openstack/openstack-manuals/commit/a0e082290c8c35346cdd484f657b5c6895b1b65a
Submitter: Jenkins
Branch: master

commit a0e082290c8c35346cdd484f657b5c6895b1b65a
Author: annegentle <email address hidden>
Date: Mon Mar 18 16:35:11 2013 -0500

    Attempts to clarify fixed_range changes in Grizzly.

    fix bug 1153459

    Change-Id: I453b9291513c736d7051ebbe0ad3f98a570f40af