kmswebrtcendpoint: fix memory leak freeing certificate_pem_file attr
kmswebrtcendpoint: fix memory leak freeing certificate_pem_file attr

Change-Id: Ibcbf663d6e47cd1e4eb4e881650c5c08418d1bac

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