MINOR: connection: don't check priv flag on free

Do not check CO_FL_PRIVATE flag to check if the connection is in session
list on conn_free. This is necessary due to the future patches which add
server connections in the session list even if not private, if the mux
protocol is the subject of HOL blocking.
diff --git a/include/haproxy/connection.h b/include/haproxy/connection.h
index 37d3f42..b99df4d 100644
--- a/include/haproxy/connection.h
+++ b/include/haproxy/connection.h
@@ -464,12 +464,10 @@
 /* Releases a connection previously allocated by conn_new() */
 static inline void conn_free(struct connection *conn)
 {
-	if (conn->flags & CO_FL_PRIVATE) {
-		/* The connection is private, so remove it from the session's
-		 * connections list, if any.
-		 */
-		if (LIST_ADDED(&conn->session_list))
-			session_unown_conn(conn->owner, conn);
+	/* If the connection is owned by the session, remove it from its list
+	 */
+	if (LIST_ADDED(&conn->session_list)) {
+		session_unown_conn(conn->owner, conn);
 	}
 	else {
 		if (obj_type(conn->target) == OBJ_TYPE_SERVER)