clientv3 logs (especially tests) were poluted with unattributed to testing.T log lines:
```
{"level":"warn","ts":"2021-04-29T12:42:11.055+0200","logger":"etcd-client","caller":"v3/retry_interceptor.go:64","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc0000fafc0/#initially=[unix://localhost:m10]","attempt":0,"error":"rpc error: code = ResourceExhausted desc = etcdserver: mvcc: database space exceeded"}
```
The reasons were 2 fold:
- Interceptors were copying logger before "WithLogger" could modify it.
- We were not propagating the loggers in a few testing contexts.
Old etcdserver which have not apply pr of #12165 will check auth token
even if the request is an Authenticate request.
If the client has a invalid auth token, it will not able to update it's
token, since the Authenticate has a invalid auth token.
This fix clear the auth token when encounter an ErrInvalidAuthToken to
talk with old version etcd servers.
Fix#12385 with #12165 and #12264
