[helm] Use Loki Canary in Helm Chart Test

[trevorwhitney]

Is your feature request related to a problem? Please describe. When installing the helm chart, how do I know that it's not only installed semantically correct (ie. k8s pods are up and running), but also that Loki is behaving correctly?

Describe the solution you'd like Include a helm chart test that utilizes the included Loki canary to test if Loki is running properly.

Describe alternatives you've considered Just use the canary dashboard, a slightly more manual process.