Allow to disable sending a refresh-mapping to master node
When a node processed an index request, which caused it to update its own mapping, then it sends that mapping to the master. While the master process it, that node receives a state that includes an older version of the mapping. Now, there is a conflict, its not bad (i.e. the cluster state will eventually have the correct mapping), but we send for a refresh just in case form that node to the master.

With a system that has extreme cases of updates and frequent mapping changes, it might make sense to disable this feature. The indices.cluster.send_refresh_mapping setting can be introduced to support that (note, this setting need to be set on the data nodes)

Note, sending refresh mapping is more important when the reverse happens, and for some reason, the mapping in the master is ahead, or in conflict, with the actual parsing of it in the actual node the index exists on. In this case, the refresh mapping will result in warning being logged on the master node.

closes #4342