Query tab cannot be disabled on Docker

[ldumont]

I'm running Puppetboard v3.4.1 using the official docker container running on Kubernetes using a home-made helm chart.

I wanted to disable the Query tab using the "ENABLE_QUERY" environment variable but it does not work because the docker_settings.py file does not handle the variable as a boolean like other variables like OFFLINE_MODE or ENABLE_CATALOG (using the coerce_bool function).

The fix should be easy, I can try to provide a PR.

[gdubicki]

Thanks for the fix @ldumont! It has been released in v3.4.2 a moment ago.