src/scanadf.c: Use scanadf_exit() when listing devices

It prevents segfault in genesys backend when exiting - the backend wants
to use a function which is already freed.

src/scanadf.c

@@ -1451,7 +1451,7 @@ main (int argc, char **argv)
 	      {
 		fprintf (stderr, "%s: sane_get_devices() failed: %s\n",
 			 prog_name, sane_strstatus (status));
-		exit (1);
+		scanadf_exit (1);
 	      }
 
 	    for (i = 0; device_list[i]; ++i)
@@ -1460,7 +1460,7 @@ main (int argc, char **argv)
 			 device_list[i]->name, device_list[i]->vendor,
 			 device_list[i]->model, device_list[i]->type);
 	      }
-	    exit (0);
+	    scanadf_exit (0);
 	  }
 
 	case 'o': outputFile = optarg; break;