The parameters are:
internalQueryColumnScanMinAvgDocSizeBytes, internalQueryColumnScanMinCollectionSizeBytes, internalQueryColumnScanMinNumColumnFilters
 
They are set in setUpServerForColumnStoreIndexTest() which is called by various core tests and aren't restored to the defaults after finishing the tests. This means we might leave the settings modified for unrelated tests. Right now it's unlikely to cause any problems because only tests that create a CSI use the settings and if a test creates a CSI it usually wants to use it. However, in general, we shouldn't be modifying the server-side parameters in Core tests.