This is what we do in lightningd, which makes memleak much more forgiving:
you can hang temporaries off cmd without getting reports of leaks (also
when send_outreq called).
We remove all the notleak() calls in plugins which worked around this!
And avoid multiple notleak labels, since both send_outreq() and
command_still_pending() can be called multiple times.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>