webrtcendpoint: Protect object against race conditions
webrtcendpoint: Protect object against race conditions

Change-Id: I3ab14a4989fe924f0273a754b4465263747cd1f3

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