WorkerPool: Execute all pending tasks before releasing
WorkerPool: Execute all pending tasks before releasing

Change-Id: Ieaeb391d76601d8026c755fd08a6deb834b2c5b5

shelsonjava/kms-core,Kurento/kms-core,ESTOS/kms-core,Kurento/kms-core,shelsonjava/kms-core,shelsonjava/kms-core,TribeMedia/kms-core,ESTOS/kms-core,ESTOS/kms-core,Kurento/kms-core,Kurento/kms-core,TribeMedia/kms-core,TribeMedia/kms-core,ESTOS/kms-core,TribeMedia/kms-core,shelsonjava/kms-core