Bug 22611: Correction for call to get create_item in EDI.pm

Bug 22611: Correction for call to get create_item in EDI.pm

There was a typo in the addition of a call to
effective_create_items causing processing to abort after adding
a single copy.

This patch reverts to using the C4::Context call as used for the
first copy created, the intended call to effective_create_items
is a wrapper around that as the field in the basket is guaranteed
to be null (its not set when we call AddBasket). Being consistent
and explicit in what we call should guard against future changes
in dependencies exposing the logic flaw

Added some comments to make logical flow of code clearer

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>