LLAP: allow ignoring the UDF check during compile time

Before UDF support is implemented, users can utilize auxjars option to package additional jars in the LLAP slider package (that was initially intended for serdes) to have some primitive UDF support. The only obstacle is that the query with UDFs will not be sent to LLAP right now; the user should be able to override that; the query with UDFs will be sent to LLAP then, and either work from a pre-packaged jar, or fail if there's no jar for this UDF (there will be no localization).

That can also be used later if desired to avoid the permanent UDF route, or for other special circumstances (like bugs in localization ).