improove OPNsenseConfig errorhandling

[rekup]

Currently, if an exception is occurring during a module execution within the context of a OPNsenseConfig object, python calls __exit__ which results in a misleading error message Config has changed. Cannot exit without saving..
If for example we try to update the config by modifying it but we did not specify become: true we get the following error message:

An exception occurred during task execution. To see the full traceback, use -vvv. The error was: RuntimeError: Config has changed. Cannot exit without saving.
fatal: [opnsense]: FAILED! 

By first checking the exception type, we can make sure there was no exception and then proceed with the check for a changed config. If there was an exception, we will return it's type and value:

TASK [test] **************************************************************************************************************************************************
An exception occurred during task execution. To see the full traceback, use -vvv. The error was: PermissionError: Exception occurred: [Errno 13] Permission denied: '/conf/config.xml'

[DonGiovanni83]

Looks Good 👍🏼