Allow cluster downgrade for version compatible versions

[johscheuer]

What would you like to be added/changed?

Currently the operator doesn't allow to downgrade versions even if they are version compatible e.g. 7.1.11 -> 7.1.9, I think we should relax this constraint and allow downgrades for version compatible versions otherwise there is no way to do a rollback of a potential bad version. Another option would be to add another setting to ignore the version check to have at least a possible way to downgrade a cluster but I would prefer to relax the check and only prevent downgrades for version incompatible versions.