Bug 11309: avoid creating duplicate numbering patterns during upgrade to 3.14.x

To test:

1/ Install Koha 3.12
2/ Create some subscriptions. Ensure you have at least two
   subscriptions with the same numbering pattern, with one of the
   keys everyX/addX/whenmorethanX/settoX set to NULL
3/ Remember this numbering pattern.
4/ Upgrade to 3.14
5/ Run updatedatabase.pl
6/ The numbering pattern is duplicated

Now repeat steps 1 to 4, then apply the patch and run
updatedatabase.pl. Numbering pattern should not be duplicated.

Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>