verify the system _qc variables are from the submission files

[leilabbb]

Assumption:
The legacy _qc variables still present in the system datasets are presumed to be from the providers' originally submitted files.

Need for Verification:

• the _qc variables in the priv_erddap files exist in the submission files
• the priv_erddap files with no _qc variables do not list _qc under the attribute ancillary_variables