staging/lustre: remove unused lvfs code

Remove the unused "lvfs" functions obd_lvfs_fid2dentry(),
ll_lookup_one_len(), l_dput(), lustre_rename(), push_ctxt(), and
pop_ctxt(). Remove the unused members of struct lvfs_run_ctxt.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>