commit 3dd4765f upstream.

...and ensure that we tear down the nfs_commit_data cache too when
unloading the module.

Cc: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
[bwh: Backported to 3.2: drop the nfs_cdata_cachep cleanup; it doesn't exist]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>