Do not allow access to LiveStreamWorker class from outside of LiveStreamThread

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>
Simplify live stream worker/thread lifecycles

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>
Merge pull request #172 from vogel/fix-171

Fix 171