add multiply, change add to use cudnn, return if not implemented

scripts/run.sh

-#./build/test/unit-test --gtest_filter=GPU.ab
+./build/test/unit-test --gtest_filter=GPU.ab
+./build/test/unit-test --gtest_filter=GPU.abc
 ./build/test/unit-test --gtest_filter=GPU.maximum
 ./build/test/unit-test --gtest_filter=GPU.minimum
 ./build/test/unit-test --gtest_filter=GPU.multiple*

src/ngraph/runtime/gpu/gpu_call_frame.cpp

@@ -31,6 +31,7 @@ runtime::gpu::GPU_CallFrame::GPU_CallFrame(std::shared_ptr<GPU_ExternalFunction>
     cublasStatus_t cublasStatus  = cublasCreate(&m_cublas_handle);
     if (cublasStatus != CUBLAS_STATUS_SUCCESS)
     {
+        std::cout << "error : " << (int)cublasStatus << std::endl;
         throw runtime_error("cuBLAS create handle failed");
     }
     cudnnStatus_t cudnnStatus = cudnnCreate(&m_cudnn_handle);