Bug 15870: potential follow up to comment #8

 Bug 15870: potential follow up to comment #8

This patch:
- makes the Koha::RecordProcessor code more clear
  by removing the unnecessary newrecord variable.
- revises the filter to be more clear about the
  expectation that operations are done directly on
  the record parameter.

TEST PLAN
---------
prove t/RecordProcessor.t
prove t/db_dependent/Filter_MARC_ViewPolicy.t
run koha qa test tools

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Works as advertised. NO koha-qa errors
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>