Before this PR, it may error like this:
```
--- FAIL: TestUpdateMember-2 (0.00s)
server_test.go:950: action =
[{ApplyConfChange:ConfChangeUpdateNode []}
{ProposeConfChange:ConfChangeUpdateNode []}], want
[{ProposeConfChange:ConfChangeUpdateNode []}
{ApplyConfChange:ConfChangeUpdateNode []}]
```
This fixes the test by recording the proposal event in time.