Issue 51157 - Reindex task may create abandoned index file
Bug Description: Recreating an index for the same attribute but changing
the case of for example 1 letter, results in abandoned indexfile.
Fix Decsription: Add a test case to a newly created 'indexes' test suite.
When we remove the index config from the backend, - remove the attribute
info from LDBM instance attributes.
https://pagure.io/389-ds-base/issue/51157
Reviewed by: firstyear, mreynolds (Thanks!)