[SPARK-7621] [STREAMING] Report Kafka errors to StreamingListeners

PR per [SPARK-7621](https://issues.apache.org/jira/browse/SPARK-7621), which makes both `KafkaReceiver` and `ReliableKafkaReceiver` report its errors to the `ReceiverTracker`, which in turn will add the events to the bus to fire off any registered `StreamingListener`s.

Author: jerluc <jeremyalucas@gmail.com>

Closes #6204 from jerluc/master and squashes the following commits:

82439a5 [jerluc] [SPARK-7621] [STREAMING] Report Kafka errors to StreamingListeners

external/kafka/src/main/scala/org/apache/spark/streaming/kafka/KafkaInputDStream.scala

@@ -135,7 +135,7 @@ class KafkaReceiver[
           store((msgAndMetadata.key, msgAndMetadata.message))
         }
       } catch {
-        case e: Throwable => logError("Error handling message; exiting", e)
+        case e: Throwable => reportError("Error handling message; exiting", e)
       }
     }
   }

external/kafka/src/main/scala/org/apache/spark/streaming/kafka/ReliableKafkaReceiver.scala

@@ -267,7 +267,7 @@ class ReliableKafkaReceiver[
           }
         } catch {
           case e: Exception =>
-            logError("Error handling message", e)
+            reportError("Error handling message", e)
         }
       }
     }