LU-12090 utils: lfs rmfid

LU-12090 utils: lfs rmfid

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.

Lustre-change: https://review.whamcloud.com/34449

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Ib22379033aca92692e0e219671ca0c2ec7893c24
Reviewed-on: https://review.whamcloud.com/35595
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>