kmsbasesdpendpoint: manage lock only at one point into set_property
kmsbasesdpendpoint: manage lock only at one point into set_property

Change-Id: Ib23f0a296541769bde3254c8500f81bf32b4eda1

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