Don't provide default values of environment variables

[jhkennedy]

We provide defaults for most of the environment variables used to differentiate the test and production stack, and most of them point to the production values. For example:

• https://github.com/ASFHyP3/its-live-monitoring/blob/develop/its_live_monitoring/src/main.py#L34
• https://github.com/ASFHyP3/its-live-monitoring/blob/develop/its_live_monitoring/src/main.py#L86

It probably makes more sense to require the environment variables or at least use the test stack values.