Add sanity check on VFAT config DB dump

Description

The dump_database routine in vfat_calibratios.py produces from DB a DataFrame with a duplicate VFAT, this creates warnings downstream as in the case of issue #43 (closed).

Related Issue

Closes #41 (closed)

How Has This Been Tested?

I checked if the output file contained any duplicate line with

uniq -c output_file -d

Types of changes

I included a line of code to drop duplicates chips before writing the VFAT calibration parameters file.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.