Leaving `index.lifecycle.indexing_complete` in place when removing the
lifecycle policy from an index can cause confusion, as if a new policy
is associated with the policy, rollover will be silently skipped.
Removing that setting when removing the policy from an index makes
associating a new policy with the index more involved, but allows ILM to
fail loudly, rather than silently skipping operations which the user may
assume are being performed.
* Adjust order of checks in WaitForRolloverReadyStep
This allows ILM to error out properly for indices that have a valid
alias, but are not the write index, while still handling
`indexing_complete` on old-style aliases and rollover (that is, those
which only point to a single index at a time with no explicit write
index)