NFSv4: Map NFS4ERR_SHARE_DENIED into an EACCES error instead of EIO

If a file OPEN is denied due to a share lock, the resulting
NFS4ERR_SHARE_DENIED is currently mapped to the default EIO.
This patch adds a more appropriate mapping, and brings Linux
into line with what Solaris 10 does.

See https://bugzilla.kernel.org/show_bug.cgi?id=43286

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org