[BUGFIX] Terminate cleanly after displaying exception message in CLI
If an exception occurred during a CLI request, it could happen that
another exception was thrown and displayed (SignalSlot, ObjectManager
not yet initialized) because the framework is in an early, unstable
state and thus cannot shutdown the bootstrap normally.
Therefore, if an exception was caught in the bootstrap, FLOW3 must exit
directly without trying to shutdown the bootstrap in the regular way.