Add setting to control servers participating in cooperative monitoring

Original description:
Customer requesting to provide a way to add/remove specific nodes participating in counting the majority votes, since nodes in

server_no_promotions

do not affect the majority calculation.

Implementation:
Added monitor setting servers_no_cooperative_monitoring_locks. The value of this setting is a comma-separated list of server names. The listed servers will not take part in cooperative monitoring. MaxScale will not acquire locks on these servers and the servers will not add to the number of locks required for majority. This setting does not affect primary server selection (i.e. Master-role), so a server in this list may be a valid target for write queries.