lightningd: fix logging of peer death.

We used level -1 to mean "append to log", but that doesn't actually
work, and results in an assert if we try to prune the logs:

	lightningd: daemon/pseudorand.c:36: pseudorand: Assertion `max' failed.

Expose logv_add and use that.

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

daemon/log.c

@@ -235,7 +235,7 @@ void log_io(struct log *log, bool in, const void *data, size_t len)
 	errno = save_errno;
 }
 
-static void do_log_add(struct log *log, const char *fmt, va_list ap)
+void logv_add(struct log *log, const char *fmt, va_list ap)
 {
 	struct log_entry *l = list_tail(&log->lr->log, struct log_entry, list);
 	size_t oldlen = strlen(l->log);
@@ -266,7 +266,7 @@ void log_add(struct log *log, const char *fmt, ...)
 	va_list ap;
 
 	va_start(ap, fmt);
-	do_log_add(log, fmt, ap);
+	logv_add(log, fmt, ap);
 	va_end(ap);
 }
 

daemon/log.h

@@ -42,6 +42,7 @@ void log_(struct log *log, enum log_level level, const char *fmt, ...)
 	PRINTF_FMT(3,4);
 void log_add(struct log *log, const char *fmt, ...) PRINTF_FMT(2,3);
 void logv(struct log *log, enum log_level level, const char *fmt, va_list ap);
+void logv_add(struct log *log, const char *fmt, va_list ap);
 
 void log_blob_(struct log *log, int level, const char *fmt,
 	       size_t len, ...)

lightningd/peer_control.c

@@ -112,7 +112,7 @@ void peer_fail(struct peer *peer, const char *fmt, ...)
 	va_start(ap, fmt);
 	log_info(peer->log, "Peer failure in %s: ",
 		 peer_state_name(peer->state));
-	logv(peer->log, -1, fmt, ap);
+	logv_add(peer->log, fmt, ap);
 	va_end(ap);
 
 	/* If we haven't reached awaiting locked, we don't need to reconnect */