Remove explicit error check at end of functions to placate lint

It's sad because this changes a regular pattern into an irregular one,
which will create spurious diffs if more work is added at the end of
the function.  Still, this is easier than fixing the lint runner to
ignore the report.

proxy/proxy.go

@@ -330,11 +330,7 @@ func copyOwnerAndPermissions(from, to string) error {
 		return nil
 	}
 
-	if err = os.Chown(to, int(moreStat.Uid), int(moreStat.Gid)); err != nil {
-		return err
-	}
-
-	return nil
+	return os.Chown(to, int(moreStat.Uid), int(moreStat.Gid))
 }
 
 func (proxy *Proxy) listen(protoAndAddr string) (net.Listener, string, error) {