add listoperation quickstart

Author: cuiy0006

google/cloud/datamigration/quickstart/quickstart.cc

@@ -59,6 +59,16 @@ int main(int argc, char* argv[]) try {
   if (!gl_res) throw std::move(gl_res).status();
   std::cout << gl_res->DebugString() << "\n";
 
+  std::cout
+      << "------------------------TEST ListOperations------------------------"
+      << std::endl;
+
+  for (auto l :
+    client.ListOperations("projects/" + std::string(argv[1]) + "/locations/" + argv[2] + "/operations", "")) {
+      if (!l) throw std::move(l).status();
+      std::cout << l->DebugString() << "\n";
+  }
+
   return 0;
 } catch (google::cloud::Status const& status) {
   std::cerr << "google::cloud::Status thrown: " << status << "\n";