SRCU uses a delayed work item.  Skip cleaning it up, and
the result is use-after-free in the work item callbacks.
Reported-by: NDmitry Vyukov <dvyukov@google.com>
Suggested-by: NDmitry Vyukov <dvyukov@google.com>
Cc: stable@vger.kernel.org
Fixes: 0eb05bf2Reviewed-by: NXiao Guangrong <xiaoguangrong.eric@gmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>