client.truncate test timed out on Mac Travis

https://travis-ci.org/DynamoRIO/dynamorio/jobs/309810811

```
32/51 Test #117: code_api|client.truncate .....................***Failed Required regular expression not found.Regex=[^thank you for testing the client interface
Hello, world!
$
] 90.16 sec
thank you for testing the client interface
```

If this happens again on just this test we can increase its timeout. It's not clear why this one would be so slow: single-instr-bbs, but it's just the hello,world app, right?