Check_MK Werk 8362: Improved error handling in case of upgrades/downgrades

ID: 8362 Title: Improved error handling in case of upgrades/downgrades Component: core Level: 2 Class: Bug Fix Version: 1.2.7i4 CMC stores its current state in versioned state files, which are only downwards-compatible. When an incompatible state file is found, we immediately terminate the monitoring core during startup. <ul> <li>When the state file version is older than the current one (e.g. after an upgrade), convert it on the fly (as previously), but keep a backup of the previous version in "state-version-XY".</li> <li>When the state file version is newer than the current one (e.g. after a downgrade), emit an error message, hinting at the backup version if there is one.</li> </ul>