[SPARK-26082][MESOS] Fix mesos fetch cache config name

## What changes were proposed in this pull request?

* change MesosClusterScheduler to use correct argument name for Mesos fetch cache (spark.mesos.fetchCache.enable -> spark.mesos.fetcherCache.enable)

## How was this patch tested?

Not sure this requires a test, since it's just a string change.

Closes #23734 from mwlon/SPARK-26082.

Authored-by: mwlon <mloncaric@hmc.edu>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

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

@@ -130,7 +130,7 @@ private[spark] class MesosClusterScheduler(
   private val queuedCapacity = conf.getInt("spark.mesos.maxDrivers", 200)
   private val retainedDrivers = conf.getInt("spark.mesos.retainedDrivers", 200)
   private val maxRetryWaitTime = conf.getInt("spark.mesos.cluster.retry.wait.max", 60) // 1 minute
-  private val useFetchCache = conf.getBoolean("spark.mesos.fetchCache.enable", false)
+  private val useFetchCache = conf.getBoolean("spark.mesos.fetcherCache.enable", false)
   private val schedulerState = engineFactory.createEngine("scheduler")
   private val stateLock = new Object()
   // Keyed by submission id