StatementTimeoutTest is flaky

```
Error:  Tests run: 40, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 14.58 s <<< FAILURE! - in com.google.cloud.spanner.connection.StatementTimeoutTest
Error:  com.google.cloud.spanner.connection.StatementTimeoutTest.testTimeoutExceptionReadWriteTransactionMultipleStatements  Time elapsed: 0.157 s  <<< FAILURE!
java.lang.AssertionError: 

Expected: is <FAILED_PRECONDITION>
     but: was <ABORTED>
	at com.google.cloud.spanner.connection.StatementTimeoutTest.testTimeoutExceptionReadWriteTransactionMultipleStatements(StatementTimeoutTest.java:405)
```

Description