NFS: Ensure that we free the rpc_task after read and write cleanups are done

NFS: Ensure that we free the rpc_task after read and write cleanups are done

commit 6db6dd7d3fd8f7c765dabc376493d6791ab28bd6 upstream.

This patch ensures that we free the rpc_task after the cleanup callbacks
are done in order to avoid a deadlock problem that can be triggered if
the callback needs to wait for another workqueue item to complete.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Weston Andros Adamson <dros@netapp.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Bruce Fields <bfields@fieldses.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>