Validate geth version in test fixture against binary used for tests

[fselmo]

What was wrong?

We've had instances where we forget to update the geth version being used in the circleCI runs and this goes unnoticed since two versions can be compatible with each other. This means we create the fixture with one version, but run it with another - and, as long as no noticeable changes have happened, this is silently unintended.

How was it fixed?

• Validate the geth binary version being used to run the tests against the version in the generated zip file for the test fixture. This version is automatically named in the zip file to be the geth version used to create the zip so it should be a decent enough check.

Todo:

• Add entry to the release notes

Cute Animal Picture

[reedsa]

Looks good.

As a follow up, we might consider updating the version as part of the fixture generation script so we don't have to remember in the future.

[pacrob]

lgtm!