Checkmk Werk 12714: hr_mem: don't crash on invalid SNMP values for `hrStorageType`

ID: 12714 Title: hr_mem: don't crash on invalid SNMP values for `hrStorageType` Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 `hrStorageType` defines the type of information provided via SNMP handled by `hr_mem`. Very often invalid values for `hrStorageType` are being provided, which leads to unhandled ValueError() exceptions. This change makes the plugin not crash on invalid values but instead return a special string "unknown" as value for `hr_type` which then can be handled properly by the checks which handle the data provided by `hr_mem`.