Do not allow to register sources until thread's context is initialized
Do not allow to register sources until thread's context is initialized

Change-Id: I074a11f8d25f4082fb02a4ef4f7f111ed0eb07d0

ESTOS/kms-core,Kurento/kms-core,TribeMedia/kms-core,shelsonjava/kms-core,shelsonjava/kms-core,TribeMedia/kms-core,KurentoLegacy/gst-kurento-plugins,ESTOS/kms-core,KurentoLegacy/gst-kurento-plugins,shelsonjava/kms-core,Kurento/kms-core,KurentoLegacy/gst-kurento-plugins,KurentoLegacy/gst-kurento-plugins,ESTOS/kms-core,Kurento/kms-core,Kurento/kms-core,TribeMedia/kms-core,shelsonjava/kms-core,TribeMedia/kms-core,ESTOS/kms-core