Noticed that the protobuf files are out of sync with ones generated by 1.2.0 protoc go plugin.

The cause for these files seem to be related to release processes, e.g. [0.9.0-beta1 preperation](https://github.com/hashicorp/nomad/commit/ecec3d38de6ca72eea68d9737d7199cf67bbfe3e#diff-da4da188ee496377d456025c2eab4e87), and [0.9.0-beta3 preperation](https://github.com/hashicorp/nomad/commit/b849d84f2fc8b47c5f5b0e387bff4fa09c3bca6e).

This restores the changes to that of the pinned protoc version and fails build if protobuf files are out of sync.  Sample failing Travis job is that of the first commit change: https://travis-ci.org/hashicorp/nomad/jobs/506285085