Revert "NFSD: fix hang in nfsd4_shutdown_callback"

This reverts commit efa8a261 which is
commit 036ac277 upstream.

It breaks the Android kernel build and can be brought back in the future
in an safe way if it is really needed.

Bug: 161946584
Change-Id: Idcb51913b49cc5d8131ba62c7e43e4246955a899
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>