[tests] Added CThread::joinable() unit test
[tests] Added CThread::joinable() unit test

ethouris/srt,Haivision/srt,ethouris/srt,Haivision/srt,Cinegy/srt,ethouris/srt,ethouris/srt,Cinegy/srt,Haivision/srt,Haivision/srt,Cinegy/srt,Cinegy/srt