Fix allowOverloading in routing

Author: optionsome

src/main/java/org/opentripplanner/service/vehiclerental/model/VehicleRentalStation.java

@@ -151,7 +151,7 @@ public Set<RentalFormFactor> getAvailableDropoffFormFactors(boolean includeRealt
     return vehicleSpacesAvailable
       .entrySet()
       .stream()
-      .filter(e -> !includeRealtimeAvailability || e.getValue() > 0)
+      .filter(e -> !includeRealtimeAvailability || allowOverloading || e.getValue() > 0)
       .map(e -> e.getKey().formFactor)
       .collect(Collectors.toSet());
   }