a new RPC_REINT_RMFID has been introduced by the patch.
it's supposed to be used with corresponding llapi_rmfid()
to unlink a batch of MDS files by their FIDs. the caller
has to have permission to modify parent dir(s) and the objects
themselves.

Change-Id: I50421d85babc74d448842acea489321a5d40052d
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34449


Reviewed-by: Li Xi <lixi@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>