aufs: tiny, revise a warning

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
aufs: possible bugfix, au_lkup_by_ino() returns ESTALE

When NFSD accesses aufs, a file-handle based upon the inode number is
passed to aufs and aufs decodes it.
If the inode is still in cache, aufs returns it immediately.
If not, aufs tries decoding the file-handle by using its parent dir
inode number. Here a problem may happen.
Suppose we have two hard-linked files under different directories,
dirA/fileA and dirB/fileB. These file's inode number are same. But the
file-handed encoded by aufs is different since aufs puts the parent dir
inode number it.
After unlinking dirA/fileA and NFSD accesses dirB/fileB, NFSD MAY pass
the file-handle for fileA. From aufs's point of view, it is incorrect
since these two file-handles are not same. But NFSD doesn't care and as
long as the inode number is same, it MAY pass the fileA'a handle to
access fileB.
To support suce case, aufs au_lkup_by_ino() returns ESTALE instead of
ENOENT.

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
Merge remote branch 'aufs3-standalone/aufs3.0/00base' into aufs3.0/10static
Merge branch 'aufs3.0/10static' into aufs3.0/11proc_map
Merge branch 'aufs3.0/00base' into aufs3.1/00base
Merge branch 'aufs3.1/00base' into aufs3.2/00base
Merge branch 'aufs3.2/00base' into aufs3.3/00base
Merge branch 'aufs3.3/00base' into aufs3.4/00base
Merge branch 'aufs3.4/00base' into aufs3.5/00base
Merge branch 'aufs3.5/00base' into aufs3.6/00base
Merge branch 'aufs3.6/00base' into aufs3.7/00base
Merge branch 'aufs3.0/10static' into aufs3.1/10static
Merge remote branch 'aufs3-standalone/aufs3.1/00base' into aufs3.1/10static
Merge branch 'aufs3.0/11proc_map' into aufs3.1/11proc_map
Merge branch 'aufs3.1/10static' into aufs3.1/11proc_map
Merge branch 'aufs3.1/10static' into aufs3.2/10static
Merge remote branch 'aufs3-standalone/aufs3.2/00base' into aufs3.2/10static
Merge branch 'aufs3.1/11proc_map' into aufs3.2/11proc_map
Merge branch 'aufs3.2/10static' into aufs3.2/11proc_map
Merge branch 'aufs3.2/10static' into aufs3.3/10static