Fixed aggregation test so it does not run against mongodb < 2.6

Author: christkv

test/functional/generator_based_tests.js

@@ -1,6 +1,7 @@
 exports['should maintain batch size between calls to receive new batches'] = {
   metadata: {
-    requires: { generators: true, topology: 'single' , node: ">6.0.0" }
+    // MongoDb must be > 2.6.0 as aggregate did not return a cursor before this version
+    requires: { generators: true, topology: 'single' , node: ">6.0.0", mongodb: ">=2.6.0" }
   },
 
   // The actual test we wish to run

test/runner.js

@@ -358,13 +358,13 @@ try {
   testFiles.push('/test/functional/operation_generators_example_tests.js');
   // Mock tests
   testFiles.push('/test/functional/command_write_concern_tests.js');
-  testFiles.push('/test/functional/replicaset_mock_tests.js');
   testFiles.push('/test/functional/collations_tests.js');
   testFiles.push('/test/functional/max_staleness_tests.js');
   testFiles.push('/test/functional/buffering_proxy_tests.js');
   testFiles.push('/test/functional/view_tests.js');
   testFiles.push('/test/functional/crud_spec_tests.js');
   testFiles.push('/test/functional/generator_based_tests.js');
+  testFiles.push('/test/functional/replicaset_mock_tests.js');
 } catch(err) {}
 
 // Add all the tests to run