[SPARK-20483][MINOR] Test for Mesos Coarse mode may starve other Mesos frameworks

## What changes were proposed in this pull request?

Add test case for scenarios where executor.cores is set as a
(non)divisor of spark.cores.max
This tests the change in
#17786

## How was this patch tested?

Ran the existing test suite with the new tests

dbtsai

Author: Davis Shepherd <dshepherd@netflix.com>

Closes #17788 from dgshep/add_mesos_test.

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

@@ -199,6 +199,40 @@ class MesosCoarseGrainedSchedulerBackendSuite extends SparkFunSuite
     verifyDeclinedOffer(driver, createOfferId("o2"), true)
   }
 
+  test("mesos declines offers with a filter when maxCores not a multiple of executor.cores") {
+    val maxCores = 4
+    val executorCores = 3
+    setBackend(Map(
+      "spark.cores.max" -> maxCores.toString,
+      "spark.executor.cores" -> executorCores.toString
+    ))
+    val executorMemory = backend.executorMemory(sc)
+    offerResources(List(
+      Resources(executorMemory, maxCores + 1),
+      Resources(executorMemory, maxCores + 1)
+    ))
+    verifyTaskLaunched(driver, "o1")
+    verifyDeclinedOffer(driver, createOfferId("o2"), true)
+  }
+
+  test("mesos declines offers with a filter when reached spark.cores.max with executor.cores") {
+    val maxCores = 4
+    val executorCores = 2
+    setBackend(Map(
+      "spark.cores.max" -> maxCores.toString,
+      "spark.executor.cores" -> executorCores.toString
+    ))
+    val executorMemory = backend.executorMemory(sc)
+    offerResources(List(
+      Resources(executorMemory, maxCores + 1),
+      Resources(executorMemory, maxCores + 1),
+      Resources(executorMemory, maxCores + 1)
+    ))
+    verifyTaskLaunched(driver, "o1")
+    verifyTaskLaunched(driver, "o2")
+    verifyDeclinedOffer(driver, createOfferId("o3"), true)
+  }
+
   test("mesos assigns tasks round-robin on offers") {
     val executorCores = 4
     val maxCores = executorCores * 2