Fix build failure due to non-direct conflict: removing import affects others

Author: HeartSaVioR

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/statefulOperators.scala

@@ -20,6 +20,8 @@ package org.apache.spark.sql.execution.streaming
 import java.util.UUID
 import java.util.concurrent.TimeUnit._
 
+import scala.collection.JavaConverters._
+
 import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.errors._