Fix _getChainedByMaster when master actually is not a master
Fix _getChainedByMaster when master actually is not a master

Problem occured in Kwc_Basic_DownloadTag_Trl_Events::onMasterMediaCacheChanged
Du to own_download DownloadTag_Trl has a DownloadTag-component beneath which results
in this event handler get called with the non-master downloadTagTrl-download component.

koala-framework/koala-framework,koala-framework/koala-framework