IndexShardRoutingTable might barf if it has handled lots of searches...

[s1monw]

A user reported this on the ML:
https://groups.google.com/forum/?fromgroups=#!topic/elasticsearch/AxRU1UQP24U

Caused by: java.lang.IndexOutOfBoundsException: index (-2) must not be negative
        at org.elasticsearch.common.base.Preconditions.checkElementIndex(Preconditions.java:306)
        at org.elasticsearch.common.base.Preconditions.checkElementIndex(Preconditions.java:285)
        at org.elasticsearch.common.collect.RegularImmutableList.get(RegularImmutableList.java:65)
        at org.elasticsearch.cluster.routing.IndexShardRoutingTable.preferNodeActiveInitializingShardsIt(IndexShardRoutingTable.java:378)
        at org.elasticsearch.cluster.routing.operation.plain.PlainOperationRouting.preferenceActiveShardIterator(PlainOperationRouting.java:210)
        at org.elasticsearch.cluster.routing.operation.plain.PlainOperationRouting.getShards(PlainOperationRouting.java:80)
        at org.elasticsearch.action.get.TransportGetAction.shards(TransportGetAction.java:80)
        at org.elasticsearch.action.get.TransportGetAction.shards(TransportGetAction.java:42)
        at org.elasticsearch.action.support.single.shard.TransportShardSingleOperationAction$AsyncSingleAction.<init>(TransportShardSingleOperationAction.java:121)
        at org.elasticsearch.action.support.single.shard.TransportShardSingleOperationAction$AsyncSingleAction.<init>(TransportShardSingleOperationAction.java:97)
        at org.elasticsearch.action.support.single.shard.TransportShardSingleOperationAction.doExecute(TransportShardSingleOperationAction.java:74)
        at org.elasticsearch.action.support.single.shard.TransportShardSingleOperationAction.doExecute(TransportShardSingleOperationAction.java:49)
        at org.elasticsearch.action.support.TransportAction.execute(TransportAction.java:63)
        at org.elasticsearch.action.support.TransportAction.execute(TransportAction.java:49)
        at org.elasticsearch.client.node.NodeClient.execute(NodeClient.java:85)
        at org.elasticsearch.client.support.AbstractClient.get(AbstractClient.java:174)
        ... 9 more

the code that causes this is:

  private int pickIndex() {
        return Math.abs(counter.incrementAndGet());
  }

which might return a negative number. Math.abs() returns -1 for Integer.MIN_VALUE which causes the AIOOB mentioned above. The usage of this method seems to be pretty broken along those lines and we might need to think about fixing this generally...