This came out in a later patch: freeing the peer->subds doesn't actually
free the subds, because they're reparented onto subd->conn, which is
a child of peer itself.
This breaks because when the peer is finally freed, destroy_subd is
called, and expects to find itself in peer->subds (but we made that
NULL when we manually freed it!).
Fix this, and make it obvious that we tal_steal it.
```
ightning_connectd: FATAL SIGNAL 11 (version v0.11.0.1-25-gbf025aa-modded)
0x55de2a1b8b94 send_backtrace
common/daemon.c:33
0x55de2a1b8c3e crashdump
common/daemon.c:46
0x7fe2be2fc08f ???
/build/glibc-SzIz7B/glibc-2.31/signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
0x55de2a1af41e destroy_subd
connectd/multiplex.c:1119
0x55de2a217686 notify
ccan/ccan/tal/tal.c:240
0x55de2a217b9d del_tree
ccan/ccan/tal/tal.c:402
0x55de2a217bef del_tree
ccan/ccan/tal/tal.c:412
0x55de2a217bef del_tree
ccan/ccan/tal/tal.c:412
0x55de2a217f39 tal_free
ccan/ccan/tal/tal.c:486
0x55de2a1aa116 peer_discard
connectd/connectd.c:1834
0x55de2a1aa38d recv_req
connectd/connectd.c:1903
0x55de2a1b9121 handle_read
common/daemon_conn.c:31
0x55de2a205a35 next_plan
ccan/ccan/io/io.c:59
0x55de2a20663d do_plan
ccan/ccan/io/io.c:407
0x55de2a20667f io_ready
ccan/ccan/io/io.c:417
0x55de2a208972 io_loop
ccan/ccan/io/poll.c:453
0x55de2a1aa736 main
connectd/connectd.c:2042
0x7fe2be2dd082 __libc_start_main
../csu/libc-start.c:308
0x55de2a1a085d ???
???:0
0xffffffffffffffff ???
???:0
```
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
37ff013c2c