plugins.ustreamtv: continue to poll the ustream API when streaming
plugins.ustreamtv: continue to poll the ustream API when streaming

chhe/streamlink,wlerin/streamlink,bastimeyer/streamlink,streamlink/streamlink,wlerin/streamlink,melmorabity/streamlink,beardypig/streamlink,gravyboat/streamlink,beardypig/streamlink,back-to/streamlink,streamlink/streamlink,gravyboat/streamlink,chhe/streamlink,bastimeyer/streamlink,javiercantero/streamlink,javiercantero/streamlink,back-to/streamlink,melmorabity/streamlink