Fixed repository and service probing (bsc#1218399)

[lslezak]

Problem

• https://bugzilla.suse.com/show_bug.cgi?id=1218399 - YaST adds a repository as a service
• Libzypp 7.31.26 and newer changed the string representation of the probing result (now returns N/A instead of NONE)
• For that reason YaST assumed the service probing succeeded (NONE = failed, anything else = success), YaST then treated the entered URL as a service URL

Solution

• Convert the libzypp probe result to string by pkg-bindings, not by libzypp
• Use libzypp enum in switch to ensure all values are handled there
• Added -Werror=switch compiler option to treat missing switch cases as errors. So when libzypp adds new values the package build will fail.

Testing

• Tested manually, repositories are now added correctly

[yast-bot]

✔️ Internal Jenkins job #47 successfully finished
✔️ Created OBS submit request #1139878