add backend protocols

[ttomzhou]

terraform-provider-tencentcloud % make testacc TESTARGS="-run TestAccTencentCloudClbListenerRule_basic"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./... -v -run TestAccTencentCloudClbListenerRule_basic -timeout 120m
?       github.com/tencentcloudstack/terraform-provider-tencentcloud    [no test files]
testing: warning: no tests to run
PASS
ok      github.com/tencentcloudstack/terraform-provider-tencentcloud/gendoc     (cached) [no tests to run]
=== RUN   TestAccTencentCloudClbListenerRule_basic
=== PAUSE TestAccTencentCloudClbListenerRule_basic
=== CONT  TestAccTencentCloudClbListenerRule_basic
--- PASS: TestAccTencentCloudClbListenerRule_basic (38.94s)
PASS
ok      github.com/tencentcloudstack/terraform-provider-tencentcloud/tencentcloud       39.850s
?       github.com/tencentcloudstack/terraform-provider-tencentcloud/tencentcloud/connectivity  [no test files]
?       github.com/tencentcloudstack/terraform-provider-tencentcloud/tencentcloud/internal/helper       [no test files]
?       github.com/tencentcloudstack/terraform-provider-tencentcloud/tencentcloud/ratelimit     [no test files]