yupdate - added suport for patching containers (bsc#1207069)

[lslezak]

Problem

• https://bugzilla.suse.com/show_bug.cgi?id=1207069
• The yupdate script refuses to work in a container, that should be allowed.

Solution

• Detect a container presence with systemd-detect-virt --container, fallback to testing some container specific files.
• If a container is detected then allow patching the system.

Testing

• Tested manually

yast-container PC:/ # yupdate patch yast/yast-packager master
Downloading https://github.com/yast/yast-packager/archive/master.tar.gz
Preparing files...
Copying to system...
Updated: /usr/share/YaST2/include/checkmedia/ui.rb
Updated: /usr/share/applications/YaST2/org.opensuse.yast.CheckMedia.desktop
Updated: /usr/share/applications/YaST2/org.opensuse.yast.SWSingle.desktop
Updated: /usr/share/applications/YaST2/org.opensuse.yast.SWSource.desktop
Updated: /usr/share/applications/org.opensuse.yast.Packager.desktop
Number of modified files: 5

[coveralls]

Coverage: 40.793% (+0.02%) from 40.77% when pulling bc076fe on yupdate_in_container into ece31be on master.

[yast-bot]

✔️ Public Jenkins job #247 successfully finished
✔️ Created OBS submit request #1057929

[yast-bot]

✔️ Internal Jenkins job #143 successfully finished
✔️ Created IBS submit request #288027