Fix UDF test

UDF invocations in udf.test should not specify a database. This is how
we switch between testing IR UDFs in the ir_function_test database and
native UDFs in the native_function_test database.

Change-Id: I09ede18f2b91440ef7a2a76b0daf41a007af2671
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3130
Reviewed-by: Skye Wanderman-Milne <skye@cloudera.com>
Tested-by: jenkins