test: suppress noise

The test suite was generating error log messages when tests would cause
error conditions.  This cluttered the output needlessly, because it
looked like test failures, but were actually tests succeeding.  Now all
log messages are suppresed during the test suite.

In addition, the XBlock runtime generates a warning about needing
IdGenerator in the future.  I'm suppressing this warning also.

Now the test suite just outputs 397 nice dots.