Switch mirror from Scenario Outline to Scenarios

Hilariously the Scenario Outline approach worked perfectly for Smokey,
but it doesn't seem to be supported by either the json formatter for
cucumber (which only shows one test result in the outline), nor the
nagios_check_cache.py script.

By changing these checks back to 4 individual scenarios, I should be
able to re-enable smokey checks in Nagios/Icinga without rewriting the
formatter or the cache checker just for this one check.
Merge pull request #84 from alphagov/non-outline-mirror-checks

Switch mirror from Scenario Outline to Scenarios