Fix in calabash-adapter

EventBusMessageListener was causing trouble during XProcSpec testing

- tests would fail silently whenever a px:message was executed
- XProc errors were never caught, instead the tests fail silently

@rdeltour I noticed you already prepared the release of pipeline-framework, but then I realized I didn't commit this fix yet. If it's not possible to include it in 1.9, that's not a tragedy.