7.3.39-0

Full Changelog: v7.3.38...v7.3.39

• fix(cupsd.conf): cups problem version >= cups-2.4.7-1.2ubuntu7.9 (#189).
• fix(cupsd.conf): require @System auth for /admin/conf (#190).
• fix(linuxmuster-release-upgrade): use linuxmuster-distupgrade to upgrade linuxmuster packages (a89bba9).
• fix(linuxmuster-release-upgrade): guard resolv.conf, apt tweak removal and linbo
  session stopping against re-runs (#191, dbf726f).
• fix(linuxmuster-release-upgrade): skip the OS release upgrade step if already done,
  so a re-run after a later-failing step doesn't abort before reaching it (#191, 2421a03).
• fix(linuxmuster-release-upgrade): don't overwrite an existing resolv.conf backup on
  a re-run (#191, 8fee984).