Bug 14932 - serials/serials-collection.pl-page is very slow. GetFullSubscription...

Bug 14932 - serials/serials-collection.pl-page is very slow. GetFullSubscription* checks permission for each serial!

Currently we have subscriptions with 300+ serials received.
It takes a lot of time to show serials-collection.pl (~20s).
This is especially troublesome when receiving serials, since after receival we get redirected to that page.

We no longer can receive daily serials in the allotted timeframe.

This quick and dirty fix prevents checking the subscription editing for each serial, but instead checks it for the first serial only.

This reduced page load time by ~18s

TEST PLAN:
1. Receive ~300 serials (or just a bunch :)  )
2. Observe the gradual slowing of the receival action.

AFTER THIS PATCH:
1. Receive ~300 serials more (or just a bunch)
2. Observe a significant performance improvement.

Signed-off-by: Paul POULAIN <paul.poulain@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Mason James <mtj@kohaaloha.com>