If for some reason the secondary index is out of date, i.e. the change
was deleted from the database but wasn't deleted from the secondary
index, it was impossible to re-index (remove) that change.
Add logic to automatically remove the change from the secondary index
if this change is requested through the Change REST API endpoint and
doesn't exist in the database.
If a user click on search result from a stale change, he will a get a
404 page and the change will be removed from the index.
To fix the problem without opening the change page, run a command like:
curl --user <user name> -X POST http://<host>:<port>/a/changes/<change id>/index
Issue: 2996
Change-Id: I1db5373e31585e99c5f45e05274d86d69b4f24e6
903be04b02