Fix: "A value is trying to be set on a copy of a slice from a DataFrame." in detect_bc_invalid.py

[antonroman]

See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
df_invalid_records['meterId'] = meter_id
detect_bc_invalid.py:39: SettingWithCopyWarning:
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead