main_common: Simplify some conditions; Add more unregister needles

[okurz]

Verification run:

openqa-clone-custom-git-refspec https://github.com/os-autoinst/os-autoinst-distri-opensuse/pull/10306 https://openqa.opensuse.org/tests/1271885 SCHEDULE=tests/installation/bootloader_uefi,tests/installation/finish_desktop

opensuse-Tumbleweed-GNOME-Live-aarch64-Build20200517-gnome-live@USBboot_aarch64 -> https://openqa.opensuse.org/t1272274

[foursixnine]

isn't this #10307?

[okurz]

hm, no. #10307 has additionally one more commit 654a243 . I could split it up differently if you prefer of course. If we would merge this PR then we simply have a single commit in #10307 left.

[foursixnine]

hm, no. #10307 has additionally one more commit 654a243 . I could split it up differently if you prefer of course. If we would merge this PR then we simply have a single commit in #10307 left.

Just treat all of them in a single PR but separate commits ;), for ease of the eyes of the reviewer