community/calamares-extensions: fix stuck install
Backport patches to fix a regression from the 1.3.0 release that cause the mobile installer to be stuck at the "new user" screen.
- Related: https://github.com/calamares/calamares-extensions/pull/26
- Related: https://github.com/calamares/calamares-extensions/issues/25
Backport this because there is no fixup release available yet (I've asked two days ago) and this is bug makes the mobile installer unusable. This adds all patches from the PR that fix the bug, as I've tested them together.