Bug 26594: Fix patrons merge problem with restrictions

Bug 26594: Fix patrons merge problem with restrictions

When merging a patron A with restriction(s) into an other patron B,
the entries of borrower_debarments are OK but the value of borrowers.debarred for patron B need to be updated.
An effect of this strange storage of restrictions in both places.

Test plan :
1) Create a patron A with a manual restriction with some date and
   comment
2) Create a patron B with no restriction
3) Merge patron A and B, keeping patron B
4) Look at patron B details page
=> Without patch you see no restriction
=> With patch you see the restriction from patron A

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>