Add useful parameters to vserver and checks

[matchaxnb]

Hello @evrardjp, Jean-Philippe,

I have added 2 parameters to your module:

vserver.quorum: allows to define the quorum weight needed to operate properly. If this quorum is not met, the sorry_server will respond instead. This allows for split brain avoidance mechanisms with a witness tie-breaker for example.

*_check.delay_loop: this parameter defines the base frequency with which health checks are done. delay_before_retry is an override for this parameter only in the case of failures. By setting delay_loop to an integer, the healthcheck will be run every that-much seconds.

I hope you like it, find it up to your standards, and merge it.

[evrardjp]

It looks good overall. I would prefer if you would amend your commit with the port though, and push again on this branch.