Reduce local retention when using Thanos storage

Reduce the local retention to 7 days when Thanos sidecars are enabled to
talk to a bucket storage system.
* Cleanup the recipe layout to put all flags in one spot.
2 jobs for <span class="ref-name">bjk/thanos_7d</span> in 3 minutes and 20 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
passed #188918927
rspec

00:01:46

 
  Lint
passed #188918928
cookstyle

00:01:34