Print type information when unknown watch error
Print type information when unknown watch error

Got

```
E0628 00:23:07.106285       1 watch.go:274] unable to encode watch object: expected pointer, but got invalid kind
```

on a production system and had no way to debug what type was being sent.

Kubernetes-commit: 307849baef076d8ee61a3b9649f9260a765f7ac0

kubernetes/apiserver,kubernetes/apiserver