zfsutils-linux recommends dkms when it's not needed

1.
$ lsb_release -rd
Description: Ubuntu 16.04.3 LTS
Release: 16.04

2.
$ apt-cache policy zfsutils-linux
zfsutils-linux:
  Installed: 0.6.5.6-0ubuntu18
  Candidate: 0.6.5.6-0ubuntu18
  Version table:
 *** 0.6.5.6-0ubuntu18 500
        500 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     0.6.5.6-0ubuntu8 500
        500 http://archive.ubuntu.com/ubuntu xenial/universe amd64 Packages

3. apt install zfsutils-linux does not install dkms,spl-dkms and dependencies since 16.04 kernel already contains zfs.ko

4. apt install zfsutils-linux installs all of the following:

dkms fakeroot gcc gcc-5 libasan2 libatomic1 libc-dev-bin libc6-dev libcc1-0 libcilkrts5 libfakeroot libfreetype6 libgcc-5-dev libgomp1 libitm1
  liblsan0 libmpx0 libquadmath0 libtsan0 libubsan0 linux-libc-dev manpages-dev spl spl-dkms

and then any kernel install/update then attempts to dkms rebuild zfs and spl even though the modules are already provided.

% dpkg -S /lib/modules/4.13.0-19-generic/kernel/zfs/zfs/zfs.ko
linux-image-4.13.0-19-generic: /lib/modules/4.13.0-19-generic/kernel/zfs/zfs/zfs.ko
% dpkg -S /lib/modules/4.13.0-19-generic/kernel/zfs/spl/spl.ko
linux-image-4.13.0-19-generic: /lib/modules/4.13.0-19-generic/kernel/zfs/spl/spl.ko

We can see from the package requirements, that it Recommends zfs-dkms, but only on Xenial. Releases newer than Xenial do not have this package requirement.

% apt-cache show zfsutils-linux
Package: zfsutils-linux
Architecture: amd64
Version: 0.6.5.6-0ubuntu18
Priority: extra
Section: admin
Source: zfs-linux
Origin: Ubuntu
Maintainer: Ubuntu Developers <email address hidden>
Original-Maintainer: Darik Horn <email address hidden>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 779
Provides: zfs
Depends: init-system-helpers (>= 1.18~), zfs-doc (= 0.6.5.6-0ubuntu18), libblkid1 (>= 2.16), libc6 (>= 2.14), libnvpair1linux, libuuid1 (>= 2.16), libuutil1linux, libzfs2linux, libzpool2linux, python3:any (>= 3.3.2-2~), python3
Recommends: zfs-dkms, zfs-zed
Suggests: samba-common-bin (>= 3.0.23), nfs-kernel-server, zfs-initramfs
Conflicts: zfs, zfs-fuse
Replaces: zfs
Filename: pool/main/z/zfs-linux/zfsutils-linux_0.6.5.6-0ubuntu18_amd64.deb
Size: 275970
MD5sum: 02ead25f1fed812980d70865da916468
SHA1: e6736c223c3b2198bba8777153836bb8d4789518
SHA256: c4ad2b81ee13072cb3f4e31fd3aed93cf66c7c50872fc542cc2425120b222eed
Homepage: https://github.com/zfsonlinux/zfs/releases/tag/zfs-0.6.5.6
Description-en: Native OpenZFS management utilities for Linux
 This package provides the zpool and zfs commands that are used to
 manage OpenZFS filesystems.
Description-md5: 7b0f98269f6c33505790717cd478736c
Supported: 5y

Here's Artful
~$ lsb_release -rd
Description: Ubuntu 17.10
Release: 17.10
$ apt-cache show zfsutils-linux
Package: zfsutils-linux
Architecture: amd64
Version: 0.6.5.11-1ubuntu3
Priority: extra
Section: admin
Source: zfs-linux
Origin: Ubuntu
Maintainer: Ubuntu Developers <email address hidden>
Original-Maintainer: Debian ZFS on Linux maintainers <email address hidden>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 1100
Provides: zfsutils
Depends: init-system-helpers (>= 1.18~), libblkid1 (>= 2.16), libc6 (>= 2.14), libnvpair1linux, libuuid1 (>= 2.16), libuutil1linux, libzfs2linux, libzpool2linux, python3:any, python3
Recommends: lsb-base, zfs-zed
Suggests: nfs-kernel-server, samba-common-bin (>= 3.0.23), zfs-initramfs | zfs-dracut
Conflicts: zfs, zfs-fuse, zutils
Filename: pool/main/z/zfs-linux/zfsutils-linux_0.6.5.11-1ubuntu3_amd64.deb
Size: 328574
MD5sum: d1ce7f5ffa75c9b46e7d5285430efff3
SHA1: 8a8ab05186b83c3f25e07d4e8fe04e60ec314640
SHA256: c462a555dda50ed12424a51158666bd3cbe1befb93a34ac81f03548051fa0b50
Homepage: http://www.zfsonlinux.org/
Description-en: command-line tools to manage OpenZFS filesystems
 The Z file system is a pooled filesystem designed for maximum data
 integrity, supporting data snapshots, multiple copies, and data
 checksums.
 .
 This package provides the zfs and zpool commands to create and administer
 OpenZFS filesystems.
Description-md5: 3b2c00b92882937cb7252c01e41d8975
Supported: 9m

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: zfsutils-linux 0.6.5.6-0ubuntu18
ProcVersionSignature: User Name 4.13.0-19.22~16.04.1-generic 4.13.13
Uname: Linux 4.13.0-19-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: amd64
Date: Wed Jan 10 22:26:33 2018
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: zfs-linux
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.sudoers.d.zfs: [deleted]