[SPARK-20078][MESOS] Mesos executor configurability for task name and labels

## What changes were proposed in this pull request?

Adding configurable mesos executor names and labels using `spark.mesos.task.name` and `spark.mesos.task.labels`.

Labels were defined as `k1:v1,k2:v2`.

mgummelt

## How was this patch tested?

Added unit tests to verify labels were added correctly, with incorrect labels being ignored and added a test to test the name of the executor.

Tested with: `./build/sbt -Pmesos mesos/test`

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Kalvin Chau <kalvin.chau@viasat.com>

Closes #17404 from kalvinnchau/mesos-config.

resource-managers/mesos/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosCoarseGrainedSchedulerBackend.scala

@@ -403,7 +403,8 @@ private[spark] class MesosCoarseGrainedSchedulerBackend(
             .setTaskId(TaskID.newBuilder().setValue(taskId.toString).build())
             .setSlaveId(offer.getSlaveId)
             .setCommand(createCommand(offer, taskCPUs + extraCoresPerExecutor, taskId))
-            .setName("Task " + taskId)
+            .setName(s"${sc.appName} $taskId")
+
           taskBuilder.addAllResources(resourcesToUse.asJava)
           taskBuilder.setContainer(MesosSchedulerBackendUtil.containerInfo(sc.conf))
 

resource-managers/mesos/src/test/scala/org/apache/spark/scheduler/cluster/mesos/MesosCoarseGrainedSchedulerBackendSuite.scala

@@ -464,6 +464,17 @@ class MesosCoarseGrainedSchedulerBackendSuite extends SparkFunSuite
     assert(!uris.asScala.head.getCache)
   }
 
+  test("mesos sets task name to spark.app.name") {
+    setBackend()
+
+    val offers = List(Resources(backend.executorMemory(sc), 1))
+    offerResources(offers)
+    val launchedTasks = verifyTaskLaunched(driver, "o1")
+
+    // Add " 0" to the taskName to match the executor number that is appended
+    assert(launchedTasks.head.getName == "test-mesos-dynamic-alloc 0")
+  }
+
   test("mesos supports spark.mesos.network.name") {
     setBackend(Map(
       "spark.mesos.network.name" -> "test-network-name"