[SPARK-19688][STREAMING] Not to read spark.yarn.credentials.file from checkpoint.

## What changes were proposed in this pull request?

Reload the `spark.yarn.credentials.file` property when restarting a streaming application from checkpoint.

## How was this patch tested?

Manual tested with 1.6.3 and 2.1.1.
I didn't test this with master because of some compile problems, but I think it will be the same result.

## Notice

This should be merged into maintenance branches too.

jira: [SPARK-21008](https://issues.apache.org/jira/browse/SPARK-21008)

Author: saturday_s <shi.indetail@gmail.com>

Closes #18230 from saturday-shi/SPARK-21008.

(cherry picked from commit e92ffe6)
Signed-off-by: Marcelo Vanzin <vanzin@cloudera.com>

Author: saturday_s

streaming/src/main/scala/org/apache/spark/streaming/Checkpoint.scala

@@ -55,6 +55,9 @@ class Checkpoint(ssc: StreamingContext, val checkpointTime: Time)
       "spark.master",
       "spark.yarn.keytab",
       "spark.yarn.principal",
+      "spark.yarn.credentials.file",
+      "spark.yarn.credentials.renewalTime",
+      "spark.yarn.credentials.updateTime",
       "spark.ui.filters")
 
     val newSparkConf = new SparkConf(loadDefaults = false).setAll(sparkConfPairs)