[SPARK-12177][Streaming][Kafka] move trait to abstract class per tdas

Author: koeninger

external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/ConsumerStrategy.scala

@@ -36,7 +36,7 @@ import org.apache.spark.annotation.Experimental
  * @tparam V type of Kafka message value
  */
 @Experimental
-trait ConsumerStrategy[K, V] {
+abstract class ConsumerStrategy[K, V] {
   /**
    * Kafka <a href="http://kafka.apache.org/documentation.htmll#newconsumerconfigs">
    * configuration parameters</a> to be used on executors. Requires "bootstrap.servers" to be set

external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/LocationStrategy.scala

@@ -34,7 +34,7 @@ import org.apache.spark.annotation.Experimental
  * Choice of location is only a preference, not an absolute; partitions may be scheduled elsewhere.
  */
 @Experimental
-sealed trait LocationStrategy
+sealed abstract class LocationStrategy
 
 private case object PreferBrokers extends LocationStrategy