…tic#51631)

Currently when an ILM policy finishes its execution, the index moves into the `TerminalPolicyStep`,
denoted by a completed/completed/completed phase/action/step lifecycle execution state.

This commit changes the behavior so that the index lifecycle execution state halts at the last
configured phase's `PhaseCompleteStep`, so for instance, if an index were configured with a policy
containing a `hot` and `cold` phase, the index would stop at the `cold/complete/complete`
`PhaseCompleteStep`. This allows an ILM user to update the policy to add any later phases and have
indices configured to use that policy pick up execution at the newly added "later" phase. For
example, if a `delete` phase were added to the policy specified about, the index would then move
from `cold/complete/complete` into the `delete` phase.

Relates to elastic#48431

Prior to the change in elastic#51631 indices were moved to the `TerminalPolicyStep` when their ILM actions
had completed. Once we switched ILM to stop in the last policy configured, these steps because
inaccessible from the policy's perspective. This meant that indices upgraded from ES prior to 7.7.0
could see the following error spammed in their logs every 10 minutes (by default) for every index in
this state:

```
[2020-04-14T15:52:23,764][ERROR][o.e.x.i.IndexLifecycleRunner] [midgar] current step [{"phase":"completed","action":"completed","name":"completed"}] for index [foo] with policy [full] is not recognized
```

This changes the runner to ignore these steps, which is what is desired anyway since the index is
already in the terminal phase.

Prior to the change in #51631 indices were moved to the `TerminalPolicyStep` when their ILM actions
had completed. Once we switched ILM to stop in the last policy configured, these steps because
inaccessible from the policy's perspective. This meant that indices upgraded from ES prior to 7.7.0
could see the following error spammed in their logs every 10 minutes (by default) for every index in
this state:

```
[2020-04-14T15:52:23,764][ERROR][o.e.x.i.IndexLifecycleRunner] [midgar] current step [{"phase":"completed","action":"completed","name":"completed"}] for index [foo] with policy [full] is not recognized
```

This changes the runner to ignore these steps, which is what is desired anyway since the index is
already in the terminal phase.

Prior to the change in #51631 indices were moved to the `TerminalPolicyStep` when their ILM actions
had completed. Once we switched ILM to stop in the last policy configured, these steps because
inaccessible from the policy's perspective. This meant that indices upgraded from ES prior to 7.7.0
could see the following error spammed in their logs every 10 minutes (by default) for every index in
this state:

```
[2020-04-14T15:52:23,764][ERROR][o.e.x.i.IndexLifecycleRunner] [midgar] current step [{"phase":"completed","action":"completed","name":"completed"}] for index [foo] with policy [full] is not recognized
```

This changes the runner to ignore these steps, which is what is desired anyway since the index is
already in the terminal phase.

Prior to the change in #51631 indices were moved to the `TerminalPolicyStep` when their ILM actions
had completed. Once we switched ILM to stop in the last policy configured, these steps because
inaccessible from the policy's perspective. This meant that indices upgraded from ES prior to 7.7.0
could see the following error spammed in their logs every 10 minutes (by default) for every index in
this state:

```
[2020-04-14T15:52:23,764][ERROR][o.e.x.i.IndexLifecycleRunner] [midgar] current step [{"phase":"completed","action":"completed","name":"completed"}] for index [foo] with policy [full] is not recognized
```

This changes the runner to ignore these steps, which is what is desired anyway since the index is
already in the terminal phase.