Address review comments

Author: Andrew Korzhuev

resource-managers/kubernetes/core/src/main/scala/org/apache/spark/deploy/k8s/Config.scala

@@ -56,7 +56,7 @@ private[spark] object Config extends Logging {
 
   val IMAGE_PULL_SECRET =
     ConfigBuilder("spark.kubernetes.imagePullSecret")
-      .doc("Specifies the Kubernetes image secret used to access private image registry.")
+      .doc("Specifies the Kubernetes secret used to access private image registry.")
       .stringConf
       .createOptional
 

resource-managers/kubernetes/core/src/main/scala/org/apache/spark/deploy/k8s/submit/steps/BasicDriverConfigurationStep.scala

@@ -17,7 +17,9 @@
 package org.apache.spark.deploy.k8s.submit.steps
 
 import scala.collection.JavaConverters._
+
 import io.fabric8.kubernetes.api.model._
+
 import org.apache.spark.{SparkConf, SparkException}
 import org.apache.spark.deploy.k8s.Config._
 import org.apache.spark.deploy.k8s.Constants._