Bug 8700 - RESERVESLIP fields not being replaced correctly

The slip RESERVESLIP is not replacing fields correctly.
C4::Reserves::ReserveSlip calls C4::Letters::GetPreparedLetter,
and passes the $reserve hashref to it for each table except branches
( which is passed the branchcode ). The problem is, if you pass a
hashref for a table, it uses that hashref for the replacing, rather
than looking up the data from the database.

Fixed by passing the correct keys for each of the tables requested.

Signed-off-by: Marc Veron <veron@veron.ch>

Tested following the test plan.
Could reproduce the bug.
After applying the patch slip printed as expected.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>

C4/Reserves.pm

@@ -2081,9 +2081,9 @@ sub ReserveSlip {
         tables => {
             'reserves'    => $reserve,
             'branches'    => $reserve->{branchcode},
-            'borrowers'   => $reserve,
-            'biblio'      => $reserve,
-            'items'       => $reserve,
+            'borrowers'   => $reserve->{borrowernumber},
+            'biblio'      => $reserve->{biblionumber},
+            'items'       => $reserve->{itemnumber},
         },
     );
 }