gtest: add scatter to combined calls and use loops (#303)

* gtest: add scatter to combined calls and use loops

* gtest: run validation inside loop

* gtest: revert small element count to 2520

* gtest: fix memory leak in validation

(cherry picked from commit b0853ccd51)

* Fix combined call UT

* Fix memory leak

* Fix alltoallv test

test/test_AllGather.hpp

@@ -25,6 +25,8 @@ namespace CorrectnessTests
 
             for (int i = 0; i < dataset.numDevices; i++)
                 memcpy(dataset.expected[i], result, dataset.NumBytes());
+
+            free(result);
         }
     };
 }