Bug 7996: Correct wrong permissions for modification log

Bug 7996: Correct wrong permissions for modification log

To test:
 1 - Create a staff patron with catalogue,borrowers,and view_system_logs
     permissions
 2 - Log in using that patron
 3 - Go to tools
 4 - Click 'Log viewer'
 5 - You get a blank page
 6 - View borrower circ screen, note you do not see 'Modification log'
 7 - Edit a borrower, note you do not see 'Modification log'
 8 - Apply patch
 9 - 'Log Viewer' should now load correctly
10 - You should see 'Modification log' tab during circ
11 - You should see 'Modification log' tab when editing patron

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>