Check if peerConnection was set previously to close it
Check if peerConnection was set previously to close it

Change-Id: Idb5e95f4edf7c404517969cf087cd86b986d852a

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