Backports fix for bsc#1180142 to SLE 12

[imobachgs]

Backport fix for bsc#1180142 to SLE 12 SP3. Please, check #1125 for details about the original fix.

Related to:

• https://github.com/yast/yast-installation/pull/1003
• https://github.com/yast/yast-update/pull/176

Manually tested upgrading from SLE 12 SP2 to SLE 12 SP4.