httpendpoint: Protect base_time from concurrent access
httpendpoint: Protect base_time from concurrent access

Change-Id: Ie280f84c537a3bd6f0ac0fe35ce37318930d7afb

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