[sles4sap] add support of 'saptune-migrate' for upgrade test from 12-* to 15-*
If we upgrade from a SLES4SAP-12-* to a SLES4SAP-15-* we have to migrate from saptune version 1 to version 2: https://openqa.suse.de/tests/3057211#step/saptune/2.
- Priority changed from Normal to Low
This ticket was set to "Normal" priority but was not updated within 730 days which is 2 times the period of the SLO for "Normal" tickets (365 days) as described on https://progress.opensuse.org/projects/openqatests/wiki/Wiki#SLOs-service-level-objectives . The ticket will be set to the next lower priority of "Low".