Work around flaky change stream test failures on mongos

This skips one test, which immediately fails on mongos due to a socket timeout on the initial aggregate.

Additionally, this bumps the number of getMore attempts for advanceCursorUntilValid.

Author: jmikola

tests/Operation/WatchFunctionalTest.php

@@ -156,6 +156,8 @@ function (array $event) use (&$lastEvent) {
 
     public function testNextResumesAfterConnectionException()
     {
+        $this->skipIfIsShardedCluster('initial aggregate command times out due to socketTimeoutMS');
+
         /* In order to trigger a dropped connection, we'll use a new client with
          * a socket timeout that is less than the change stream's maxAwaitTimeMS
          * option. */
@@ -1600,7 +1602,7 @@ private function isStartAtOperationTimeSupported()
         return server_supports_feature($this->getPrimaryServer(), self::$wireVersionForStartAtOperationTime);
     }
 
-    private function advanceCursorUntilValid(Iterator $iterator, $limitOnShardedClusters = 5)
+    private function advanceCursorUntilValid(Iterator $iterator, $limitOnShardedClusters = 10)
     {
         if (! $this->isShardedCluster()) {
             $iterator->next();