[BUG][Weighted Routing] weighted shard routing state is not maintained across search requests

[anshu1106]

Describe the bug
In search requests using weighted shard routing if weights are put as (1,1,0) then the distribution of requests to data nodes is not in proportion to assigned weights. Found that data nodes in zone A had twice the requests than data nodes in zone B though weight is 1 for both the zones.

To Reproduce
Steps to reproduce the behavior:

1. Set weighted shard routing weights using PUT api call

PUT /_cluster/routing/awareness/zone/weights
{ 
     "weights":
     {
       "zone_A": "1", 
       "zone_B": "1", 
       "zone_C": "0"
     }
     "_version" : -1
}

4. Make 100 search requests
5. Distribution of search request across nodes is not correct. Data nodes in zone A has twice the number of requests than data nodes in zone B which doesn't honor weighted round robin

Expected behavior
Distribution of request should be in ratio of assigned weights

Additional context
The bug got introduced with #5072 in OS 2.5 release.