Remove some stack traces from sbt test output

This change gets rid of some of the output printed to stdout while running `sbt test`. 

1. Stack trace of the form
```
13/07/07 11:23:13.827 WARN StaticChannelPipeline: An exception was thrown by an exception handler.
java.util.concurrent.RejectedExecutionException
```
are now sent to SLF4J by initializing the `InternalLoggerFactory` used by StaticChannelPipeline in Netty . http://grepcode.com/file/repo1.maven.org/maven2/org.jboss.netty/netty/3.2.5.Final/org/jboss/netty/channel/StaticChannelPipeline.java#StaticChannelPipeline

2. Minor changes to make `CheckpointSuite` and `DriverSuite` not print anything to stdout as well.