doc: fs manpage fixes

doc: fs manpage fixes

 - fs_whichcell: Fix formatting typo

 - fs_setcbaddr: Change -host to -addr

 - Add missing -help to fs_setcbaddr and fs_rxstatproc

 - fs_getfid: Add missing -literal to synopsis

 - fs_exportafs: List on/off options in single =item. Doing this in
   two separate consecutive =items confuses the manpage generator.

 - fs_exportafs: Add missing -clipags and -pagcb

Change-Id: I4e986543292f1000fc00456fde486d7da573c9c3
Reviewed-on: http://gerrit.openafs.org/10396
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>