LSICORR: Ensure filename PV updates correctly

As a user of the SANS-DLS on zoom I want to be able to use the LSI correlator. We got a support call saying that the correlator IOC was struggling to connect to the hardware. We found that the thread which updates the current filename PV with the run number and current title every 10 seconds (`THREADPOOL.submit(self.update_output_file)`) was causing the IOC to crash.

As a temporary fix we disabled this thread and informed the scientists that the current filename displayed in the OPI would appear out of date. Re-enabling this is part of #5303

This issue might have been fixed by https://github.com/ISISComputingGroup/genie_python/pull/215, which has not been deployed on zoom but might have been on the developer's machine.