We use this technique for the other tags, so use it here too.
This was drawn to my attention when I made more than 10 channels in a
block, and the string changed length:
Valgrind error file: valgrind-errors.31415
==31415== Conditional jump or move depends on uninitialised value(s)
==31415== at 0x4C35E20: bcmp (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==31415== by 0x11A624: queue_broadcast (broadcast.c:40)
==31415== by 0x118D93: handle_pending_cannouncement (routing.c:704)
==31415== by 0x1109E3: handle_txout_reply (gossip.c:1796)
==31415== by 0x111177: recv_req (gossip.c:1955)
==31415== by 0x136723: next_plan (io.c:59)
==31415== by 0x137220: do_plan (io.c:387)
==31415== by 0x13725E: io_ready (io.c:397)
==31415== by 0x138B97: io_loop (poll.c:305)
==31415== by 0x111352: main (gossip.c:2022)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
8fcb45c1b2