installcheck: delete requests confused by own multibuild flavors

[DimStar77]

Very often we see delete requests for packages that have a _multibuild flle; often times, one of the flavor depends on the other flavors

installcheck (and also cleanup_rings) do not take into account that they are linked together.

A typical scenario: delete req of rust1.62; nothing in the distro uses this anymore, except rust1.62:test (it's own test suite) deleting rust1.62 obviously makes rust1.62:test disappear as well

The test should be enhanced to take the entire set of packages to disappear into account (and for sure it should also check that all flavors binaries are not used by anything else in the distro - in case that is not done yet)

[DimStar77]

sample installcheck report:

Generated from http://botmaster.suse.de:8153/go/tab/build/detail/AdiChecker.Factory/42208/Run/1/Run#tab-console

rust1.62 is still a build requirement of:

- rust1.62:test

[Vogtinator]

Fixed with #2945.