Move freeing printer objects from cpdbPrinterCallback() to cpdbOnPrinterRemoved() for API consistence (#83)

Fixes #79

Straightens the logic of the API. The object is created in cpdbOnPrinterAdded() so it shouls be freed in  cpdbOnPrinterRemoved() and not in cpdbPrinterCallback().

NOTE: This can require changes in frontends.

Author: prab0007al

cpdb/cpdb-frontend.c

@@ -83,7 +83,6 @@ void cpdbPrinterCallback(cpdb_frontend_obj_t *f, cpdb_printer_obj_t *p, cpdb_pri
 
     case CPDB_CHANGE_PRINTER_REMOVED:
         g_message("Removed printer %s : %s!\n", p->name, p->backend_name);
-        cpdbDeletePrinterObj(p);
         break;
 
     case CPDB_CHANGE_PRINTER_STATE_CHANGED:
@@ -129,6 +128,7 @@ void cpdbOnPrinterRemoved(GDBusConnection *connection,
     g_variant_get(parameters, "(ss)", &printer_id, &backend_name);
     cpdb_printer_obj_t *p = cpdbRemovePrinter(f, printer_id, backend_name);
     f->printer_cb(f, p, CPDB_CHANGE_PRINTER_REMOVED);
+    cpdbDeletePrinterObj(p);
 }
 
 void cpdbOnPrinterStateChanged(GDBusConnection *connection,