Fix MPI build issue with bazel

While trying to build tensorflow with MPI through:
```
...
$ bazel build -s --verbose_failures --config=opt //tensorflow/tools/pip_package:build_pip_package
```
, the following failure happens:
```
tensorflow/contrib/mpi_collectives/kernels/mpi_ops.cc:76:18: error: 'se' does not name a type
 using StatusOr = se::port::StatusOr<T>;
                  ^
tensorflow/contrib/mpi_collectives/kernels/mpi_ops.cc:139:28: error: 'StatusOr' was not declared in this scope
 typedef std::function<void(StatusOr<Tensor>)> CommunicationDoneCallback;
...
...
```

This fix addresses the build failures for MPI build.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>