cross error with settings "search.remote.cluster_two.skip_unavailable": true

[zqc0512]

es 5.6.x
i have 200+ node with 3 clusters will use cross cluster search.
in es 5 this setting don't have setting with "search.remote.cluster_two.skip_unavailable": true about cross cluster settings

it can add in es 5.6.11?
with some orther promble i can't update to es 6.x

the es 6 one index only have one type ,
but in my env the date have many type from one flume, if update to es 6, one day will have 400+ indices with 10TB, the bulk speed will not better than with es 5.

thanks.

Describe the feature:

Elasticsearch version (bin/elasticsearch --version):

Plugins installed: []

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Description of the problem including expected versus actual behavior:

Steps to reproduce:

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[jasontedor]

Sorry but #27182 was a major enhancement and we do not make such changes in patch releases, especially in the non-current major series which is in maintenance mode. When we put a series in maintenance mode, our focus is on stability and we therefore only backport critical fixes.

[zqc0512]

@jasontedor if i buy the elastic support can add the function in es 5.6.11?