kmselement: Add pad when agnostic exists
kmselement: Add pad when agnostic exists

Change-Id: I4c4ff4a5e3d5c41e6d5fe7eb37d0c2c9b5799951

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