QC re-run is not cleaning quality_control_log

[ocehugo]

The quality_control_log variable in the netcdf/toolbox is currently missing to be reseted when the user request the QCmethods to be re-run.

This was spotted when testing different despiking tests - after re-run of QC tests is requested, older runs are still registred and exported in the netcdf. All in all, quality_control_log is behaving as a "quality_control_session_log" instead.

Requirements:

• reset the string when the user requested to re-run the QC tests.

[ocehugo]

Move to the next milestone so we don't delay the release anymore. When data is imported from NetCDF the current branch is deleting previous qcs.