GEODE-9441: Reduce Nested func test thread count (#6708)

Change `NestedFunctionExecutionDistributedTest` to create fewer threads.

The test creates a number of threads that is a multiple of
`MAX_FE_THREADS`. On a CI machine, the default value of `MAX_FE_THREADS`
can be very high, causing this test to create thousands of threads. This
can leave the system unable to create threads for other processes, which
in turn can cause Gradle processes or other tests to fail or hang.

This test now sets `MAX_FE_THREADS` to a lower value (100), which
suffices for the purpose of the test, and results in greatly reduced
consumption of threads.

Co-authored-by: Dale Emery <demery@vmware.com>

geode-core/src/distributedTest/java/org/apache/geode/internal/cache/execute/NestedFunctionExecutionDistributedTest.java

@@ -55,7 +55,11 @@
 @Category(FunctionServiceTest.class)
 @SuppressWarnings("serial")
 public class NestedFunctionExecutionDistributedTest implements Serializable {
-
+  // Limit the number of FE threads for this test. On a CI machine, the default value can be very
+  // large, which can cause this test to overwhelm the system and prevent other tests and processes
+  // from creating threads.
+  private static final String TEST_MAX_FE_THREADS = "100";
+  private static final String MAX_FE_THREADS_PROPERTY = "DistributionManager.MAX_FE_THREADS";
   private String uniqueName;
   private String regionName;
   private String hostName;
@@ -99,6 +103,7 @@ private int createServerCache() throws IOException {
     Properties properties = new Properties();
     properties.setProperty(ConfigurationProperties.SERIALIZABLE_OBJECT_FILTER,
         "org.apache.geode.internal.cache.execute.NestedFunctionExecutionDistributedTest*");
+    System.setProperty(MAX_FE_THREADS_PROPERTY, TEST_MAX_FE_THREADS);
     cacheRule.createCache(properties);
     CacheServer cacheServer = cacheRule.getCache().addCacheServer();
     cacheServer.setPort(0);
@@ -111,6 +116,7 @@ private int createServerCache() throws IOException {
 
   private void createClientCache(int port, int functionTimeout) {
     System.setProperty(GEMFIRE_PREFIX + "CLIENT_FUNCTION_TIMEOUT", String.valueOf(functionTimeout));
+    System.setProperty(MAX_FE_THREADS_PROPERTY, TEST_MAX_FE_THREADS);
     clientCacheRule.createClientCache();
     PoolManager.createFactory().addServer(hostName, port).setRetryAttempts(0).create(uniqueName);
   }