Fix direct system calling when using log parameter propagation.

This fixes an issue when attempting to run MythSystem commands directly,
outside of a system shell, without any custom arguments, and selecting
to propagate logging arguments. The issue that occurs is that the
logging arguments are incorrectly added to the executable path, meaning
the command cannot be successfully run.

mythtv/libs/libmythbase/mythsystem.cpp

@@ -110,7 +110,7 @@ void MythSystem::SetCommand(const QString &command,
     // add logging arguments
     if (GetSetting("PropagateLogs"))
     {
-        if (m_args.isEmpty())
+        if (GetSetting("UseShell") && m_args.isEmpty())
         {
             m_command += logPropagateArgs;
             if (!logPropagateQuiet())