[SPARK-3571] Spark standalone cluster mode doesn't work.

I think, this issue is caused by #1106

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2436 from sarutak/SPARK-3571 and squashes the following commits:

7a4deea [Kousuke Saruta] Modified Master.scala to use numWorkersVisited and numWorkersAlive instead of stopPos
4e51e35 [Kousuke Saruta] Modified Master to prevent from 0 divide
4817ecd [Kousuke Saruta] Brushed up previous change
71e84b6 [Kousuke Saruta] Modified Master to enable schedule normally

core/src/main/scala/org/apache/spark/deploy/master/Master.scala

@@ -489,23 +489,24 @@ private[spark] class Master(
     // First schedule drivers, they take strict precedence over applications
     // Randomization helps balance drivers
     val shuffledAliveWorkers = Random.shuffle(workers.toSeq.filter(_.state == WorkerState.ALIVE))
-    val aliveWorkerNum = shuffledAliveWorkers.size
+    val numWorkersAlive = shuffledAliveWorkers.size
     var curPos = 0
+
     for (driver <- waitingDrivers.toList) { // iterate over a copy of waitingDrivers
       // We assign workers to each waiting driver in a round-robin fashion. For each driver, we
       // start from the last worker that was assigned a driver, and continue onwards until we have
       // explored all alive workers.
-      curPos = (curPos + 1) % aliveWorkerNum
-      val startPos = curPos
       var launched = false
-      while (curPos != startPos && !launched) {
+      var numWorkersVisited = 0
+      while (numWorkersVisited < numWorkersAlive && !launched) {
         val worker = shuffledAliveWorkers(curPos)
+        numWorkersVisited += 1
         if (worker.memoryFree >= driver.desc.mem && worker.coresFree >= driver.desc.cores) {
           launchDriver(worker, driver)
           waitingDrivers -= driver
           launched = true
         }
-        curPos = (curPos + 1) % aliveWorkerNum
+        curPos = (curPos + 1) % numWorkersAlive
       }
     }