[BUG] proto_tcp: fix address binding on remote source

Mark Brooks reported that commit 1b4b7c broke tproxy in 1.5-dev6. Nick
Chalk tracked the issue down to a missing address family setting in
tcp_bind_socket() which resulted in a failure to use get_addr_len().
This issue is 1.5-specific.
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 13ea210..e6d6c58 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -132,6 +132,7 @@
 #endif
 	if (flags) {
 		memset(&bind_addr, 0, sizeof(bind_addr));
+		bind_addr.ss_family = remote->ss_family;
 		switch (remote->ss_family) {
 		case AF_INET:
 			if (flags & 1)