distributor: add comments
distributor: add comments

Add in some additional comments around more complex areas of the code
so as to make the code easier to read and understand.

Signed-off-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>

phermansson/dpdk,phermansson/dpdk,phermansson/dpdk,phermansson/dpdk