[test/degenerate-pen] Add missing return value.

Carl - he likes to test us occasionally to make sure we're paying
attention. Well, that's the excuse I use...

test/degenerate-pen.c

@@ -95,6 +95,8 @@ draw (cairo_t *cr, int width, int height)
 	cairo_stroke (cr);
     }
     cairo_restore (cr);
+
+    return CAIRO_TEST_SUCCESS;
 }
 
 int