Checkmk Werk 13468: mrpe: Do not crash upon invalid metrics

ID: 13468 Title: mrpe: Do not crash upon invalid metrics Component: Checks & agents Level: 1 Class: New feature Version: 2.1.0i1 In Checkmk versions prior to 2.0, invalid performance data strings passed by the MRPE plugin have been ignored. In Checkmk 2.0 the parsing would find those invalid strings, and crash upon them. This is generally the desired behaviour (see <a href=https://docs.checkmk.com/latest/en/devel_check_plugins.html#errors>… documentation</a> for a rationale). However, since MRPE comprises a lot of different plugins, an all-or-nothing approach is rather inconvenient. We now parse everything as good as we can, and issue an <tt>UNKNOWN</tt> state for the affected service.