Introduce "stickiness" of errors/warnings in SNMP
Currently, if an error or warning occurs for a short time (some seconds), our monitoring tool (Grafana) will not notice. It is proposed to introduce a config parameter which would allow to prolong appearance of errors/warnings (possibly separate config for each level). This would be useful, for example, in the context of delock warning (#215 (closed)) that now occurs only during one SNMP read after the delock cnt is increased.