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

Change-Id: I9d4dfe87d5420e8d8a8df56d3f5f7419bc14904b

Kurento/kms-elements,shelsonjava/kms-elements,TribeMedia/kms-elements,shelsonjava/kms-elements,Kurento/kms-elements,TribeMedia/kms-elements,shelsonjava/kms-elements,TribeMedia/kms-elements,Kurento/kms-elements