checkstyle: make warnings count as violations
checkstyle: make warnings count as violations

Aka, lower the severity required to fail to warning from error.

dhalperi/batfish,batfish/batfish,arifogel/batfish,intentionet/batfish,dhalperi/batfish,batfish/batfish,arifogel/batfish,arifogel/batfish,batfish/batfish,intentionet/batfish,intentionet/batfish,dhalperi/batfish,intentionet/batfish,intentionet/batfish