Suppress expected OracleIT stack traces

OracleIT intentionally triggers the following stack trace in the build. It should be suppressed, if possible, because it can be confused with an actual error.

```
Running org.apache.fluo.integration.impl.OracleIT
2016-08-04 15:39:04,312 [server.AbstractNonblockingServer$FrameBuffer] ERROR: Unexpected throwable while invoking!
java.lang.IllegalStateException: Received timestamp request but Oracle is not leader
at org.apache.fluo.core.oracle.OracleServer.getTimestampsImpl(OracleServer.java:240)
at org.apache.fluo.core.oracle.OracleServer.getTimestamps(OracleServer.java:220)
at org.apache.fluo.core.thrift.OracleService$Processor$getTimestamps.getResult(OracleService.java:269)
at org.apache.fluo.core.thrift.OracleService$Processor$getTimestamps.getResult(OracleService.java:252)
at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:39)
at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:39)
at org.apache.thrift.server.AbstractNonblockingServer$FrameBuffer.invoke(AbstractNonblockingServer.java:516)
at org.apache.thrift.server.Invocation.run(Invocation.java:18)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
2016-08-04 15:39:05,937 [server.AbstractNonblockingServer$FrameBuffer] ERROR: Unexpected throwable while invoking!
java.lang.IllegalStateException: Received timestamp request but Oracle is not leader
at org.apache.fluo.core.oracle.OracleServer.getTimestampsImpl(OracleServer.java:240)
at org.apache.fluo.core.oracle.OracleServer.getTimestamps(OracleServer.java:220)
at org.apache.fluo.core.thrift.OracleService$Processor$getTimestamps.getResult(OracleService.java:269)
at org.apache.fluo.core.thrift.OracleService$Processor$getTimestamps.getResult(OracleService.java:252)
at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:39)
at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:39)
at org.apache.thrift.server.AbstractNonblockingServer$FrameBuffer.invoke(AbstractNonblockingServer.java:516)
at org.apache.thrift.server.Invocation.run(Invocation.java:18)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
2016-08-04 15:39:11,707 [server.AbstractNonblockingServer$FrameBuffer] ERROR: Read a frame size of 1633837924, which is bigger than the maximum allowable buffer size for ALL connections.
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 13.349 sec - in org.apache.fluo.integration.impl.OracleIT
```