Btrfs: should add a permission check for setfacl

CVE-2010-2071

On btrfs, do the following
------------------
  # file: aaa
  # owner: user1
  # group: user1
  user::rw-
  group::rw-
  other::r--
  # file: aaa
  # owner: user1
  # group: user1
  user::rwx           <- successed to setfacl
  group::rw-
  other::r--
------------------
but we should prohibit it that user2 changing user1's acl.
In fact, on ext3 and other fs, a message occurs:
  setfacl: aaa: Operation not permitted

This patch fixed it.
Signed-off-by: Shi Weihua <shiwh@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
(cherry-picked from commit 2f26afba

 upstream)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>