message: Add missing attributes
  Summary: Ref  T22234
  Test Plan: Test passes
  Reviewers: #tensorflow, hakons, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved
  Maniphest Tasks: T22234
diff: @@ -15,6 +15,7 @@ limitations under the License.
  #include "tensorflow/compiler/plugin/poplar/driver/passes/multi_conv_fixer.h"
  +#include "tensorflow/compiler/plugin/poplar/driver/backend_config.pb.h"
  #include "tensorflow/compiler/plugin/poplar/driver/tools/custom_ops/multi_conv.h"
  #include "tensorflow/compiler/plugin/poplar/driver/tools/matcher_predicates.h"
  #include "tensorflow/compiler/xla/service/hlo_casting_utils.h"
  @@ -50,6 +51,12 @@ ENTRY e {
  TF_ASSERT_OK_AND_ASSIGN(auto module,
  ParseAndReturnVerifiedModule(hlo, config));
  + auto root = module->entry_computation()->root_instruction();
  + auto attributes = root->frontend_attributes();
  + auto* map = attributes.mutable_map();
  + (*map)[FrontendAttributeId_Name(OPTION_FLAGS)] = "{}";
  + root->set_frontend_attributes(attributes);
  +
  TF_ASSERT_OK_AND_ASSIGN(bool changed, MultiConvFixer().Run(module.get()));
  EXPECT_TRUE(changed);
  EXPECT_EQ(module->entry_computation()->instruction_count(), 4);
  @@ -84,10 +91,16 @@ ENTRY e {
  TF_ASSERT_OK_AND_ASSIGN(auto module,
  ParseAndReturnVerifiedModule(hlo, config));
  + auto root = module->entry_computation()->root_instruction();
  + auto attributes = root->frontend_attributes();
  + auto* map = attributes.mutable_map();
  + (*map)[FrontendAttributeId_Name(OPTION_FLAGS)] = "{}";
  + root->set_frontend_attributes(attributes);
  +
  TF_ASSERT_OK_AND_ASSIGN(bool changed, MultiConvFixer().Run(module.get()));
  EXPECT_TRUE(changed);
  EXPECT_EQ(module->entry_computation()->instruction_count(), 9);
  - auto root = module->entry_computation()->root_instruction();
  + root = module->entry_computation()->root_instruction();
  EXPECT_EQ(root->opcode(), HloOpcode::kAdd);
  EXPECT_EQ(root->operand(0)->operand(0), root->operand(1)->operand(0));
  auto multi_conv = Cast<HloMultiConvInstruction>(root->operand(0)->operand(0));
  