Ensure iocage checks that snapshot exists before destroying it
In iocage if we want to remove a snapshot, we don't check if it exists. We should first check and if it exists then remove it.
root@freenas[~]# iocage snapremove -n snaptest/root cloned_jail_renamed could not find any snapshots to destroy; check snapshot names. Command '['zfs', 'destroy', '-r', '-f', 'vol1/iocage/jails/cloned_jail_renamed@snaptest/root']' returned non-zero exit status 1.
We risk breaking removal of snapshots in iocage for a jail
If a snapshot doesn't exist, we should raise an exception appropriately and it should be made sure that we haven't broken removal of snapshots. So an existing snapshot should be removed and ensured that it works