Bug 21975: Avoid unnecessary substitutions in automatic item modification by age

Bug 21975: Avoid unnecessary substitutions in automatic item modification by age

Automatic item modification by age cronjob is based on rules with conditions and substitutions.
When substitution value is equal to actual item value, the code should not call C4::Items::ModItem. It adds unnecessary action log and entry in zebraqueue.
With a rule than can impact all catalogue you can explode your database with action logs.

Test plan :
1) Run prove t/db_dependent/Items/AutomaticItemModificationByAge.t
2) Define a item modification by age with no condition
3) Run several times misc/cronjobs/automatic_item_modification_by_age.pl
4) Check it creates only one entry in action_logs and zebraqueue

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>