Yicheng Qin bf3057e5bd raft: extend wait timeout in TestMultiNodeAdvance
This fixes the failure met in semaphore CI:

```
--- FAIL: TestMultiNodeAdvance-2 (0.01s)
		multinode_test.go:458: expect Ready after Advance, but there is
		no Ready available
```
2015-10-23 12:08:24 -07:00
..
2015-09-03 15:32:25 -07:00
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2015-09-21 06:13:33 +02:00
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