RFE: Revert configuration if Ansible cannot reach the host anymore

[tyll]

Idea by @thom311 in #33 to use the checkpoint feature to revert changes in case the host cannot be reached anymore after the configuration. A possible idea would be not to remove the checkpoint but send it back to the ansible host and destroy it in a later step to test that the host can still be reached.

[tyll]

Closed as duplicate of #194 that specifies the approach in a clearer way.