PIC-34: Rename default configmap name to be consistent with mapr-kubernetes (apache#374)

Author: Oleksandr Mukhopad

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

@@ -303,7 +303,7 @@ private[spark] object Config extends Logging {
     ConfigBuilder("spark.mapr.cluster.configMap")
       .doc("Name of the mapr cluster config map")
       .stringConf
-      .createWithDefault("mapr-cluster-configmap")
+      .createWithDefault("mapr-cluster-cm")
 
   val MAPR_CLUSTER_USER_SECRETS =
     ConfigBuilder("spark.mapr.user.secrets")