kmsplayerendpoint: Finish internal thread execution on dispose call
kmsplayerendpoint: Finish internal thread execution on dispose call

Change-Id: Ibe03bcfc656e7aab8e27bbb69d5846834d6bf4a7

ESTOS/kms-core,TribeMedia/kms-core,KurentoLegacy/gst-kurento-plugins,shelsonjava/kms-core,shelsonjava/kms-core,Kurento/kms-core,KurentoLegacy/gst-kurento-plugins,ESTOS/kms-core,shelsonjava/kms-core,Kurento/kms-core,shelsonjava/kms-core,ESTOS/kms-core,TribeMedia/kms-core,TribeMedia/kms-core,KurentoLegacy/gst-kurento-plugins,Kurento/kms-core,TribeMedia/kms-core,ESTOS/kms-core,KurentoLegacy/gst-kurento-plugins,Kurento/kms-core