* luks_device: fix remove_keyslot not working when set to 0
* luks_device: fix module outputting 'ok' when trying to add a key that is already present in another keyslot
* luks_device: fix breaking unit tests
* luks_device: Duplicate key test case code cleanup
* luks_device: Fix testing of LUKS passphrases when only testing one key slot
* luks_device: Fix testing of LUKS passphrases when only testing one key slot
* luks_device: Add changelog fragment for PR #710
* luks_device: Update changlog fragment