Function destroy_snapshots does not work

[IvanClement]

The function destroy_snapshots does not work on debian Stretch, because the '-r' switch is not supported by tail.

I'm going to investigate how to improve the function.

Regards.

Below the error message received:
tail : option invalide -- 'r'
Saisissez « tail --help » pour plus d'informations.
tail : option invalide -- 'r'
Saisissez « tail --help » pour plus d'informations.
missing dataset argument
usage:
destroy [-fnpRrv] <filesystem|volume>
destroy [-dnpRrv] <filesystem|volume>@[%][,...]
destroy <filesystem|volume>#

For the property list, run: zfs set|get

For the delegated permission list, run: zfs allow|unallow