Future versions of redis will validate this port number causing the tests
relying on this to fail with:
```
Redis::CommandError:
ERR Invalid master port
```
Also change from an IPv4 address that might feasibly be in use to an IPv6
random ULA address that almost *certainly* won't be.
It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
David Taylor
Loïc Guitaut
Phil Pirozhkov
Michael Brown
Jarek Radosz