Packaging cleanup

* Declare compliance with policy 4.4.1
* Set Rule-Requires-Root: no
* Stay at debhelper compat level 11, level 12 breaks the build

debian/control

@@ -1,7 +1,7 @@
 Source: clevis
 Maintainer: Christoph Biedl <debian.axhn@manchmal.in-ulm.de>
 Homepage: https://github.com/latchset/clevis
-Standards-Version: 4.2.1
+Standards-Version: 4.4.1
 Vcs-Browser: https://git.in-ulm.de/cbiedl/clevis
 Vcs-Git: https://git.in-ulm.de/cbiedl/clevis.git
 Build-Depends: debhelper (>= 11~),
@@ -22,6 +22,7 @@ Build-Depends: debhelper (>= 11~),
     tang,
     tpm2-tools,
 Priority: optional
+Rules-Requires-Root: no
 Section: net
 
 Package: clevis