Setting empty string for video tag src field on dispose
Setting empty string for video tag src field on dispose

Change-Id: I01bc1fa58972cd12c5ce58ed732d6bb0b8d56d51

Kurento/kurento-utils-js,lcamacho/kurento-utils-js,KurentoLegacy/kws-utils,Kurento/kurento-utils-js,shelsonjava/kurento-utils-js,lcamacho/kurento-utils-js,shelsonjava/kurento-utils-js,Kurento/kurento-utils-js