BUG/MINOR: quic: Wrong ->accept() error handling

Really signal the caller that ->accept() has failed if the session could not
be initialized because conn_complete_session() has failed. This is the case
if the mux could not be initialized too.
When it fails an ->accept() must returns -1 in case of resource shortage.
diff --git a/src/quic_sock.c b/src/quic_sock.c
index 1a5cf69..011b93a 100644
--- a/src/quic_sock.c
+++ b/src/quic_sock.c
@@ -69,8 +69,6 @@
 	if (conn_complete_session(cli_conn) >= 0)
 		return 1;
 
-	return 0;
-
  out_free_sess:
 	/* prevent call to listener_release during session_free. It will be
 	* done below, for all errors. */
@@ -83,7 +81,7 @@
 	conn_free(cli_conn);
  out:
 
-	return 0;
+	return -1;
 }
 
 /*