BUG/MINOR: sock: fix sock_create_server_socket

Set stream_err value as SF_ERR_NONE, if obtained socket fd has passed all
common runtime and configuration related checks.

'.connect()' method implementation in higher protocol layers requires Stream
Error Flag as the return value. So, at the socket layer, we need to pass to
sock_create_server_socket() a variable to set this flag, because syscalls and
some socket options checks are convenient to performe at the socket layer.

src/sock.c

@@ -326,7 +326,7 @@ int sock_create_server_socket(struct connection *conn, struct proxy *be, int *st
 	if (conn->flags & CO_FL_OPT_TOS)
 		sock_set_tos(sock_fd, conn->dst, conn->tos);
 
-	stream_err = SF_ERR_NONE;
+	*stream_err = SF_ERR_NONE;
 	return sock_fd;
 }