main/zfs-lts: upgrade to 2.1.2
All zfs packages in 3.15.0 are built from version 2.1.2 except the kernel module zfs-lfs
which is built from 2.1.1. This seems to have been overlooked, I don't think it was intentional. Upgrading the kernel module to 2.1.2 fixes #13198 (closed) which is otherwise still present in release 3.15.0.