[Bugfix] Build metadata store go proto and metadata store service go proto error

#### What happened:
Checkout master branch code, and build metadata store go proto and metadata store service go proto error

#### What you expected to happen:
Build metadata store go proto and metadata store service go proto sucessfully

#### How to reproduce it (as minimally and precisely as possible):
```shell
➜ ml-metadata git:(master) ✗ bazel build -s -c opt --define grpc_no_ares=true //ml_metadata/proto:metadata_store_go_proto
INFO: Analysed target //ml_metadata/proto:metadata_store_go_proto (0 packages loaded, 0 targets configured).
...
ERROR: /data/tongchao/work/go/src/github.com/google/ml-metadata/ml_metadata/proto/BUILD:57:1: Generating Descriptor Set proto_library //ml_metadata/proto:metadata_store_proto_copy failed (Exit 1) protoc failed: error executing command bazel-out/host/bin/external/com_google_protobuf/protoc '--descriptor_set_out=bazel-out/k8-opt/genfiles/ml_metadata/proto/metadata_store_proto_copy-descriptor-set.proto.bin' ... (remaining 5 argument(s) skipped)

Use --sandbox_debug to see verbose messages from the sandbox
google/protobuf/struct.proto: File not found.
ml_metadata/proto/metadata_store.proto:19:1: Import "google/protobuf/struct.proto" was not found or had errors.
ml_metadata/proto/metadata_store.proto:27:5: "google.protobuf.Struct" is not defined.
Target //ml_metadata/proto:metadata_store_go_proto failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.335s, Critical Path: 0.07s
INFO: 0 processes.
FAILED: Build did NOT complete successfully

➜ ml-metadata git:(master) ✗ bazel build -s -c opt --define grpc_no_ares=true //ml_metadata/proto:metadata_store_service_go_proto
ERROR: /data/tongchao/.cache/bazel/_bazel_tongchao/953894ff544ae0ec51997aa49a4c9758/external/io_bazel_rules_go/proto/BUILD.bazel:21:1: no such package '@org_golang_google_grpc//codes': The repository '@org_golang_google_grpc' could not be resolved and referenced by '@io_bazel_rules_go//proto:go_grpc'
ERROR: Analysis of target '//ml_metadata/proto:metadata_store_service_go_proto' failed; build aborted: no such package '@org_golang_google_grpc//codes': The repository '@org_golang_google_grpc' could not be resolved
INFO: Elapsed time: 0.096s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (0 packages loaded, 0 targets configured)
```

#### Anything else we need to know?:
* Relate issue
[Update google_ml_metadata to v0.27.0 version, resulting in compilation failure](https://github.com/kubeflow/metadata/issues/257)

#### Environment:
- Bazel version (use `bazel version`):
```shell
➜ ml-metadata git:(master) ✗ bazel version
Build label: 0.24.1
Build target: bazel-out/k8-opt/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar
Build time: Tue Apr 2 16:29:26 2019 (1554222566)
Build timestamp: 1554222566
Build timestamp as int: 1554222566
```
- Cloud provider or hardware configuration:
- OS (e.g: `cat /etc/os-release`):
```shell
➜ ml-metadata git:(master) ✗ cat /etc/os-release
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"
```
- Kernel (e.g. `uname -a`):
```shell
➜ ml-metadata git:(master) ✗ uname -a
Linux localhost 3.10.0-957.el7.x86_64 #1 SMP Thu Nov 8 23:39:32 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
```
- Install tools:
- Others: