Fixed evaluating the available package versions (bsc#1151824)

[lslezak]

The Problem

• https://bugzilla.suse.com/show_bug.cgi?id=1151824
• https://openqa.suse.de/tests/3406978#step/resolve_dependency_issues/2
• Fixed a crash when trying to download a non-existing package
• The PackageDownloader::FetchError exception is raised when YaST wants to download a package from source -1 (that actually means the package is installed in the system, not available on any medium)

The Fix

• I could not reproduce locally, but checking the code I found that the problem is in using the Pkg.PkgProperties call which does not allow to specify the package more precisely, it can return the result for any package instance
• Tested manually, at least no regression was found
• Reported by openQA, we should see quickly if this fix helps
• Additionally I switched from memory hungry Pkg.PkgProperties to the more efficient Pkg.Resolvables call
• 4.2.27

[coveralls]

Coverage increased (+0.006%) to 28.945% when pulling 2a0b27d on package_status_fix_bsc1151824 into ab055d7 on master.

[yast-bot]

✔️ Public Jenkins job #136 successfully finished
✔️ Created OBS submit request #736429

[yast-bot]

✔️ Internal Jenkins job #36 successfully finished
✔️ Created IBS submit request #202650