Run tests in Docker environment w/o logging to stdout

[matthew-li]

Currently, tests may be run from web or app-shell, but because STREAM_LOGS_TO_STDOUT is True, the log messages generated during tests severely clutter test output.

Some assorted possibilities:

• Override that setting in the various base test classes.
• Make a new image test-shell that has some log files pre-created that can be written to instead.
• Override the LOGGING setting in the various base test classes so that logs are written to these files instead.