Fix issue with too many live stream threads

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>
Remove old threads from MediaDownload

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>
Reduce number of active threads

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>
Merge pull request #176 from vogel/fix-173

Fix 173