Since PR #37358 we vendor a fork of ugorji/go, see commit 09921ca for details. We need to get rid of the fork and switch to upstream.

As far as I remember it was impossible because the package api changed in an incompatible way so I had to backport a fix.

From a quick look into git history it looks like

• it is needed by etcd (which is needed by libkv, which is needed by libnetwork);
• it wasfirst vendored in PR Bump to latest libkv + dependencies #16863 (commit 7078e7d);
• updated in PR Bump etcd to 2.3.2 #23220 (commit f02ffd9).