By default, Elasticsearch auto-creates indices when a document is
submitted to a non-existent index. There is a setting that allows users
to disable this behavior. However, this setting should not apply to
system indices, so that Elasticsearch modules and plugins are able to
use auto-create behavior whether or not it is exposed to users.

This commit constructs the AutoCreateIndex object with a reference to
the SystemIndices object so that we bypass the check for the user-facing
autocreate setting when it's a system index that is being autocreated.

We also modify the logic in TransportBulkAction to make sure that if a
system index is included in a bulk request, we don't skip the
autocreation step.