make lrc act like rr under low load

[prymitive]

with this patch lrc acts more like rr algorithm when request rate is very low. Side effect is that when one adds new node to long running cluster, then lrc will try to catch new node request count up to other nodes value, but since it will only happen during low request rate, than I don't consider it as an issue

[unbit]

i will make some test but i think having a 'second round' of checks (when more than one node has the lowest refcnt) is a better approach.

[prymitive]

I'm sure that it's not the best way and I do not insist on this particular code, but I've been running my FastRouters with it since yesterday and in case of my workloads it works really well.
Having second loop adds more logic and I don't think that it will be noticeably better in real workloads. The only thing second loop will add is even greater fairness, but since this is under low request rate (more than one node reference is 0) then differences will be minimal.
As always I leave it to Your judgement.

[unbit]

i will merge it, honestly this is how lrc should behave. For different scenario we can develop alternatives algo.