Configurable monitor check failures

It would be great to have configurable monitor check failures in MaxScale, especially when we want to put the monitor_interval to a low value. Right now if a monitor fails a check it marks the server as down as soon as the check is failed.

I envision something similar as ProxySQL has:

If a host misses mysql-monitor_ping_max_failures pings in a row, MySQL_Monitor informs MySQL_Hostgroup_Manager that the node is unreacheable and that should immediately kill all connections. It is important to note that in case a connection to the backend is not available, MySQL_Monitor will first try to connect in order to ping, therefore the time to detect a node down could be one of the two:

mysql-monitor_ping_max_failures * mysql-monitor_connect_timeout
mysql-monitor_ping_max_failures * mysql-monitor_ping_timeout

A monitor_max_failures parameter with a default of 1 would be an improvement of this feature.