Bug 5795 Update the database as follow-up If sys pref

Bug 5795 Update the database as follow-up If sys pref

ReservesControlBranch has null then update the table to
insert a PatronLibrary as value

To Test:
1) Go to mysql use koha database
2) select * from systempreferences where variable = 'ReservesControlBranch'; Check if value set to ItemHomeLibrary.
+-----------------------+-----------------+-------------------------------+-------------------------------------------------+--------+
| variable              | value           | options                       | explanation                                     | type   |
+-----------------------+-----------------+-------------------------------+-------------------------------------------------+--------+
| ReservesControlBranch | PatronLibrary   | ItemHomeLibrary|PatronLibrary | Branch checked for members reservations rights. | Choice |
+-----------------------+-----------------+-------------------------------+-------------------------------------------------+--------+

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>