NFS: Clean up do_callback_layoutrecall()

Removing the dprintk()s lets us simplify the function by removing the
else condition entirely and returning the status of
initiate_{file,bulk}_draining() directly.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>