Remove -settime/RXAFS_GetTime client support

Remove -settime/RXAFS_GetTime client support

Remove the -settime option from afsd, and any code for making
RXAFS_GetTime calls in libafs. Server probes have been replaced by
calls to RXAFS_GetCapabilities, and the actual functionality of
synchronizing the system clock has been superseded by other systems
like NTP. Issue a warning for all code paths that try to enable
-settime support.

Historical note: the code that this commit is removing contains bugs.
Do not simply revert this commit to turn on -settime support again.

Change-Id: Id291f5f88b1ad84594706f2a1a02a933dddd0cb9
Reviewed-on: http://gerrit.openafs.org/5787
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>