Add possibility to exclude node from load balancer based on error rate

[ksysoev]

In current implementation of load balancer doesn't care if node alive or not. We should implement logic to exclude node from load balancing if consequent error counter exceeded defined threshold.
In suspended node state load balancer should periodically check liveness status of the suspended nodes, and return them back into load-balancing if get success result.
If none of node has alive status, load balancer should consider all of them as equal and just distribute load between them.