Sort out how server env is set

[VirginiaDooley]

Issue and Steps to Reproduce

We are setting environment throughout the app with different methods; this needs to be:

consistent throughout, except where it relates to Lambda functions
used in conjunction with override_settings in tests so that subsequent tests do not fail

https://stackoverflow.com/questions/2059482/temporarily-modify-the-current-processs-environment/34333710#34333710

Ref #5050