Remove AI_ADDRCONFIG getaddrinfo hints flag for listening sockets.

Because, according to RFC 3493, that will cause getaddrinfo to
overlook the ::1 loopback if there's not some other interface with
a global IPv6 address.  The rationale being that the flag helps
prevent unnecessary AAAA lookups, but since I set AI_NUMERICHOST,
lookups aren't going to happen anyway.

Also update the IPv6 Bro communication test to get it to work more
reliably.

src/RemoteSerializer.cc

@@ -4023,7 +4023,7 @@ bool SocketComm::Listen()
 
 	hints.ai_protocol = IPPROTO_TCP;
 	hints.ai_socktype = SOCK_STREAM;
-	hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG | AI_NUMERICHOST;
+	hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST;
 
 	char port_str[16];
 	modp_uitoa10(listen_port, port_str);

testing/btest/istate/bro-ipv6-socket.bro

@@ -1,11 +1,11 @@
 # @TEST-GROUP: comm
 #
-# @TEST-REQUIRES: ifconfig | grep -q "inet6 ::1"
+# @TEST-REQUIRES: ifconfig | grep -q -E "inet6 ::1|inet6 addr: ::1"
 #
 # @TEST-EXEC: btest-bg-run recv bro -b ../recv.bro
 # @TEST-EXEC: btest-bg-run send bro -b ../send.bro
 # @TEST-EXEC: btest-bg-wait -k 20
-# 
+#
 # @TEST-EXEC: btest-diff recv/.stdout
 # @TEST-EXEC: btest-diff send/.stdout
 
@@ -46,6 +46,10 @@ event remote_connection_handshake_done(p: event_peer)
 	{
 	print fmt("handshake done with peer: %s", p$host);
 	event my_event("hello world");
+	}
+
+event remote_connection_closed(p: event_peer)
+	{
 	terminate();
 	}