Add unitest for factorization machine layer with sparse input

paddle/gserver/tests/test_LayerGrad.cpp

@@ -2444,8 +2444,8 @@ void testFactorizationMachineLayer(InputType type, bool useGpu) {
 TEST(Layer, FactorizationMachineLayer) {
   for (auto useGpu : {false, true}) {
     testFactorizationMachineLayer(INPUT_DATA, useGpu);
-    testFactorizationMachineLayer(INPUT_SPARSE_FLOAT_VALUE_DATA, useGpu);
   }
+  testFactorizationMachineLayer(INPUT_SPARSE_FLOAT_VALUE_DATA, false);
 }
 
 int main(int argc, char** argv) {