Bug 17466: Show number of outstanding issues when checking in

Bug 17466: Show number of outstanding issues when checking in

Test plan:
1) Apply patch
2) Checkout more then one item to a borrower
3) Check one of that items
4) Note, that on in returns table there is a button with number of
outstanding issues in patron column. The button should take you to checking
out page
5) When the outstanding issues count is 0, there is no button

Signed-off-by: Radek Šiman <rbit@rbit.cz>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>