Missmatching OS versions prevent snapshot creation

[mdellweg]

When installing a host with Debian 9.1 that is reported as 9.4 later, you can no longer create snapshots.
The rather confusing error message is:
Validation failed: Partition Table Preseed default does not belong to Debian 9.4 operating system, Medium Debian Mirror does not belong to Debian 9.4 operating system

[mdellweg]

Hopefully the problem is fixed by:
theforeman/foreman#5610