logfile.html: Added code to prevent parallel load
logfile.html: Added code to prevent parallel load

- Reduced refresh rate to 300ms
- Added code to prevent parallel AJAX requests (kills Rasp performance)

In avg, one server execution of a 304 Not modified request take about 1,15 sec each
Removing GetOpt::Long (only for testing, not checked in) reduced time to 1,04 sec.

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