Only print the exception messages for CLI connection issues.

https://issues.jboss.org/browse/WFCORE-133
Should this have some formatting? That is instead of

```
org.jboss.as.cli.SomeException
java.io.IOException
java.net.ConnectException
```

there would be

```
org.jboss.as.cli.SomeException
    caused by: java.io.IOException
    caused by: java.net.ConnectException
```