[master] Revert "Update "deb" packaging to use "dh_installsystemd""

[thaJeztah]

This reverts commit f9ac2f6 (#686), as it unfortunately won't work with ubuntu 18.04

We can work on this later, to see if we can find a suitable workaround

[thaJeztah]

Well... of course, why not?

+ git -C src/github.com/docker/cli fetch --update-head-ok --depth 1 origin refs/heads/master:refs/heads/master
fatal: unable to access 'https://github.com/docker/cli.git/': Failed to connect to github.com port 443: Connection timed out
make: *** [Makefile:55: checkout-cli] Error 128
script returned exit code 2

[thaJeztah]

whoop; green now

[tianon]

To unpack this a little bit more, I think to be able to reconsider what I was trying to do in #686 we'd really need to either drop support for bionic (not great as it's still very popular with users) or make it work somehow with compat level 10.