Fix a possible crash when sending the HUP signal.

When the HUP signal is sent while some outgoing connections have not been made
yet, or are being retried, a NULL pointer could be dereferenced resulting in
tinc crashing. We fix this by more careful handling of outgoing_ts, and by
deleting all connections that have not been fully activated yet at the HUP
signal is received.

src/net.h

@@ -98,6 +98,7 @@ typedef struct outgoing_t {
 	struct config_t *cfg;
 	struct addrinfo *ai;
 	struct addrinfo *aip;
+	struct event *event;
 } outgoing_t;
 
 extern list_t *outgoing_list;