Lee Hinman 119f8ed9f0 Correctly enable _all for older 5.x indices
When we disabled `_all` by default for indices created in 6.0, we missed adding
a layer that would handle the situation where `_all` was not enabled in 5.x and
then the cluster was updated to 6.0, this means that when the cluster was
updated the `_all` field would be disabled for 5.x indices and field values
would not be added to the `_all` field.

This adds a compatibility layer for 5.x indices where we treat the default
enabled value for the `_all` field to be `true` if unset on 5.x indices.

Resolves #25068
2017-06-08 14:37:44 -06:00
..