LevelLoader : fix double manifest request on mono quality live playlist
LevelLoader : fix double manifest request on mono quality live playlist

related to https://github.com/mangui/flashls/issues/421

jlacivita/flashls,vidible/vdb-flashls,fixedmachine/flashls,clappr/flashls,fixedmachine/flashls,mangui/flashls,tedconf/flashls,NicolasSiver/flashls,mangui/flashls,NicolasSiver/flashls,hola/flashls,vidible/vdb-flashls,jlacivita/flashls,neilrackett/flashls,codex-corp/flashls,tedconf/flashls,neilrackett/flashls,codex-corp/flashls,clappr/flashls,hola/flashls