Bug 16635: [QA Follow-up] Eliminate some global package vars

Bug 16635: [QA Follow-up] Eliminate some global package vars

[1] $branch is only related to line 123 as fallback.
[2] $width moved to a constant; sub width is not used.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Tested the corresponding plugin in item editor.
Test t/db_dependent/Barcodes.t and Barcodes_ValueBuilder.t still pass.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 4fc8b3d6cf6453f7ff550b9fbde1a7f6315dd066)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>