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

`gotestsum` has user friendlier output that emits final summary, also it can emit junit xml file for
automated analysis instead of current format that should significantly
ease automated analysis of CI.

Allow it to fail for now with the goal of making it the default build in
the future.

The new Travis Trusty image uses node 8 (latest LTS) as the default.
Node 8 is incompatible with some modules used for the UI.

This package no longer exists so trying to install it broke our build.
It has been renamed docker-ce.

I apologize in advance for the rather long PR, but unfortunately there
is not an easy way to break this up into smaller chunks. This separates
the agent configuration into smaller, more consumable pieces just like
the job specification.