Fix services in statistics.json.
Currently there is a bug in configurate that reports incorrectly the services settings if they are set as ENV variables, instead of diaspora.yml settings.
This commit works around that issue by changing the way the setting is fetched.
Fix statistics_presenter_spec
Merge pull request #5256 from jaywink/fix-services-statistics

Fix services in statistics.json.
Reset dynamic configuration after each example in the testsuite