Remove extraneous parens around return arguments.

This resolves #540.

test/integration/extent.c

@@ -174,7 +174,7 @@ TEST_END
 
 int
 main(void) {
-	return (test(
+	return test(
 	    test_extent_manual_hook,
-	    test_extent_auto_hook));
+	    test_extent_auto_hook);
 }