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: I40e092ca9ccf0012706f7ed3ea71508cf262d90a
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>