client: flag in cachemanager if rmtsys is enabled

client: flag in cachemanager if rmtsys is enabled

when processing "fs sysname" on a client, a rmtsys-related
checks are executed by default. These prevent a user with gid
2748 and 2750 (0xabc and 0xabe) from executing this command.
Add a new flag inside the cachemanager for the rmtsys-
functionality. This flag is set through a new ioctl by the afsd
on startup.

Reviewed-on: http://gerrit.openafs.org/10245
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit db1de98ecf6fd22b9c36b3ba284984f03cb0ae35)

Change-Id: Ia2a367e4675782a681b4f6efd6365da482adfab8
Reviewed-on: https://gerrit.openafs.org/12607
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: Stephan Wiesand <stephan.wiesand@desy.de>