pipeline: add drop port for each pipeline

pipeline: add drop port for each pipeline

An additional output port is now implicitly created for every pipeline
to serve as the packet drop port. Up to now, the drop port had to be
explicitly created for each pipeline.

Signed-off-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
Signed-off-by: Yogesh Jangra <yogesh.jangra@intel.com>