kmsbufferinjector: Add property to modify the wait time
kmsbufferinjector: Add property to modify the wait time

Setting by default to 2. The element waits twice the default framerate

Change-Id: I2f9f689aa3b1d404605f2a515bc4c261ea0a10ce

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