[gtk] (8 commits) ...Merge branch 'ci-installed-tests' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  4fed323... testsuite: Fix installed tests (*)
  aea253b... ci: Add gnome-desktop-testing to images (*)
  501b2b4... ci: Enable sudo in the image (*)
  3a9b824... ci: Use newer fedora image (*)
  7cf61e6... ci: Add a build that runs installed tests (*)
  28a9fa2... installed-tests: Fix the icontheme test (*)
  5ecf143... cups: Don't emit a warning if we can't talk to avahi (*)
  be03613... Merge branch 'ci-installed-tests' into 'master'

(*) This commit already existed in another branch; no separate mail sent