!squash rfofmsg.cc: Refactor set_command

Use a new OFP_BUFFER_NONE constant rather than specifying UINT32_MAX
!squash rfofmsg.cc: Refactor ofp_mask conversion

Expose interface for full IPv4 mask, not CIDR
!squash nox/rfproxy: Add new OpenFlow interface

Convert IPv4 mask as full mask, not CIDR mask (which was incorrect)