message: redis: fix merge race
diff: @@ -473,7 +473,7 @@ protected:
  // No change.
  expectRedisResolve();
  - resolve_timer_->callback_();
  + resolve_timer_->invokeCallback();
  EXPECT_CALL(*cluster_callback_, onClusterSlotUpdate(_, _)).Times(1).WillOnce(Return(false));
  expectClusterSlotResponse(twoSlotsMastersWithReplica());
  expectHealthyHosts(std::list<std::string>(
  @@ -482,7 +482,7 @@ protected:
  // Remove 2nd shard.
  expectRedisResolve();
  EXPECT_CALL(membership_updated_, ready());
  - resolve_timer_->callback_();
  + resolve_timer_->invokeCallback();
  EXPECT_CALL(*cluster_callback_, onClusterSlotUpdate(_, _)).Times(1);
  expectClusterSlotResponse(singleSlotMasterReplica("127.0.0.1", "127.0.0.2", 22120));
  expectHealthyHosts(std::list<std::string>({"127.0.0.1:22120", "127.0.0.2:22120"}));
  @@ -819,7 +819,7 @@ TEST_F(RedisClusterTest, RedisReplicaErrorResponse) {
  for (uint64_t i = 1; i < (1 << 3); i++) {
  std::bitset<3> replica_flags(i);
  expectRedisResolve();
  - resolve_timer_->callback_();
  + resolve_timer_->invokeCallback();
  if (replica_flags.all()) {
  EXPECT_CALL(membership_updated_, ready());
  EXPECT_CALL(*cluster_callback_, onClusterSlotUpdate(_, _)).Times(1).WillOnce(Return(false));
  