Drop tests package from debian builds

[tbrisker]

Tests aren't expected to run in production anyways, no point in
packaging them. We don't package them in RPMS as well.

(cherry picked from commit c298716)

For plugin updates, please indicate which repos this should be built into:

• Nightly
• 1.21
• 1.20

See Foreman's plugin maintainer documentation for more information.

---

[ekohl]

I'm not in favor of dropping a package from a released version since I suspect the old version will remain available in the archive and cause weird issues. @mmoll @evgeni probably know more.

[tbrisker]

ok, we'll go with 1.21.2 to fix this.