Caching of meta user does not seem to work

Caching of meta user does not seem to work. Even when a user should be cached, the auth service will still get the user from the meta API.

The following lines of test code should work without an gock request for Alice, but fail because the meta API caching is not working: https://github.com/influxdata/kapacitor/blob/3407c75c78a6c0ac6a5ca32949d12d9a0e60b57e/integrations/metaauth_test.go#L182-L187

Start with the referenced test in integrations/metaauth_test.go, especially lines 182-187, and run the relevant integration test. Trace why the auth service still requests Alice from the meta API despite caching. Done means those lines pass without a gock request for Alice.

Written by the indexing model from the issue text.