Abandoning RabbitMQ, lower test timeout, codecov.

Fixing codecov in CI conf files. Running `setup.py test` multiple times
overwrites the previous run's coverage file, so codecov was only
gathering coverage for the last test run. Running codecov after every
test command if exit is 0.

Looks like RabbitMQ cannot really be used as a locking service.
single_instance is not compatible with RabbitMQ, however the Celery
class should work fine with it.

20 second timeout for Celery worker thread is excessive, lowering to 10
seconds. This is only reached locally during exploratory testing.