[HOTFIX] Remove cleaning of UDFs

Author: marmbrus

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ScalaUdf.scala

@@ -23,9 +23,6 @@ import org.apache.spark.util.ClosureCleaner
 case class ScalaUdf(function: AnyRef, dataType: DataType, children: Seq[Expression])
   extends Expression {
 
-  // Clean function when not called with default no-arg constructor.
-  if (function != null) { ClosureCleaner.clean(function) }
-
   type EvaluatedType = Any
 
   def nullable = true