Remove unnecessary _make_port function in BSN UTs

The Big Switch unit tests had unnecessary copies of the
_make_port function to allow the binding:host_id field to
be set. This was already possible with the existing _make_port
call through the use of kwargs so the extra function wasn't
necessary.

Change-Id: I88679173117739f628ae289636b5cdea10417e6c
Merge "Remove unnecessary _make_port function in BSN UTs"