9pfs: local: remove: use correct path component

Commit a0e640a8 introduced a path processing error.
Pass fstatat the dirpath based path component instead
of the entire path.

Signed-off-by: Bruce Rogers <brogers@suse.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
(cherry picked from commit 790db7ef)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>