etcd/etcdserver
Yicheng Qin 27170e67b9 etcdserver: specify timeout caused by leader election
Before this PR, the timeout caused by leader election returns:

```
14:45:37 etcd2 | 2015-08-12 14:45:37.786349 E | etcdhttp: got unexpected
response error (etcdserver: request timed out)
```

After this PR:

```
15:52:54 etcd1 | 2015-08-12 15:52:54.389523 E | etcdhttp: etcdserver:
request timed out, possibly due to leader down
```
2015-08-12 16:53:18 -07:00
..
2015-08-08 05:31:35 -07:00
2015-06-11 14:22:14 -07:00
2015-06-09 13:53:07 -07:00
2015-06-24 12:42:40 -07:00