libplugin-pay: make sure get_gossmap calls are balanced by put_gossmap.

This will become important when we apply localmods to the gossmap at these points.

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

plugins/pay.c

@@ -1307,4 +1307,5 @@ int main(int argc, char *argv[])
 				  "Disable multi-part payments.",
 				  flag_option, &disablempp),
 		    NULL);
+	io_poll_override(libplugin_pay_poll);
 }