Elasticsearch v7.0 changed the behavior of max concurrent shard
requests and the default to 5. v5.6 and before 7.0 the default
is 256. This adds some additional behavior given certain
version is selected when configure the datasource to set
default max concurrent shard requests.
Changing from a version pre-v7.0+ to v7.0+ sets max
concurrent shard requests to 5.
Changing from a version v7.0+ to a pre-v7.0 sets max
concurrent shard requests to 256.

Fixes #17454