beadm destroy worked for me in Build 122

After cleanup of the IPS Cache as described here, I still had the 11G used in a snapshot for
a previous build, so I had to destroy the previous boot environment.

beadm destroy Build_118

worked for me without a problem. There were no error messages about not
being able to delete a ZFS snapshot as described in the update to Build 121.

Now the 11G are back for usage.