Merge f87d1c95 ("exec: Move would_dump into flush_old_exec")

The change to exec is relevant to the cleanup work I have been doing.

Merge it here so that I can build on top of it, and so hopefully
that other merge logic can pick up on this and see how to deal
with the conflict between that change and my exec cleanup work.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>