Revert "NFSD: fix hang in nfsd4_shutdown_callback"

This reverts commit abed6802 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: Id7324f989a8b5e86e44b7dc56fff4a5144c65106
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>