Python unittest intercepts stdout and stderr however qemurunner sets
up a streamhandler before that interception occurs, hence the messages
spam the unittest output.
By moving the logging init to the class init time, we use the unittest
stdout/stderr and this means unittest can only show the log output upon
failure. This cleans up the selftest and testimage output whilst still
showing logging upon failure.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
