[PATCH] nfsd: check for read-only exports before setting acls

We must check for MAY_SATTR before setting acls, which includes checking
for read-only exports: the lower-level setxattr operation that
eventually sets the acl cannot check export-level restrictions.

Bug reported by Martin Walter <mawa@uni-freiburg.de>.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>