feature request: pause delta queue handling on read only indexes

[nvdk]

Currently mu-search will log an error for failed updates, like so:

2022-08-11T05:24:53.096530944Z Response: 403 Forbidden
2022-08-11T05:24:53.096538700Z {"error":{"root_cause":[{"type":"cluster_block_exception","reason":"index [eada71e71bcfbab392833b72365714e3] blocked by: [FORBIDDEN/12/index read-only / allow delete (api)];"}],"type":"cluster_block_exception","reason":"index [eada71e71bcfbab392833b72365714e3] blocked by: [FORBIDDEN/12/index read-only / allow delete (api)];"},"status":403}

it will retry a few times (I think, but need to confirm) and after that drop the update and continue onto the next one. In this case it might be better to pause delta queue processing and only continue when the read only has been resolved.