DEBUG_LEVEL env variable is overridden by default config

[pselden]

Repro steps:

1. Change the deployment to use:

env:
- name: DEBUG_LEVEL
   value: TRACE

2. Restart Dinghy
3. Observe in the logs that it is still using INFO

This is because

dinghy/cmd/dinghy.go

Line 71 in 3c33937

logLevelStr := util.GetenvOrDefault("DEBUG_LEVEL", "info")

right afterwards it checks for the settings in the config file. However there's a default of INFO set for that, so it will never be unset.