lightningd: free timers on shutdown.

Direct leak of 1024 byte(s) in 2 object(s) allocated from:
    #0 0x7f4c84ce4448 in malloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10c448)
    #1 0x55d11b782c96 in timer_default_alloc ccan/ccan/timer/timer.c:16
    #2 0x55d11b7832b7 in add_level ccan/ccan/timer/timer.c:166
    #3 0x55d11b783864 in timer_fast_forward ccan/ccan/timer/timer.c:334
    #4 0x55d11b78396a in timers_expire ccan/ccan/timer/timer.c:359
    #5 0x55d11b774993 in io_loop ccan/ccan/io/poll.c:395
    #6 0x55d11b72322f in plugins_init lightningd/plugin.c:1013
    #7 0x55d11b7060ea in main lightningd/lightningd.c:664
    #8 0x7f4c84696b6a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x26b6a)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/lightningd.c

@@ -854,6 +854,7 @@ int main(int argc, char *argv[])
 	/* FIXME: pay can have children off tmpctx which unlink from
 	 * ld->payments, so clean that up. */
 	clean_tmpctx();
+	timers_cleanup(&ld->timers);
 	tal_free(ld);
 	opt_free_table();