util.c: avoid dead store to "flag"

* src/util.c (virExecDaemonize): Change flag |= VAR to "flag | VAR".

src/util.c

@@ -663,7 +663,7 @@ int virExecDaemonize(virConnectPtr conn,
 
     ret = virExecWithHook(conn, argv, envp, keepfd, retpid,
                           infd, outfd, errfd,
-                          flags |= VIR_EXEC_DAEMON,
+                          flags | VIR_EXEC_DAEMON,
                           hook, data, pidfile);
 
     /* __virExec should have set an error */