[BUG]Can't initialize detector after disable/re-enable AD plugin

[kaituo]

What is the bug?
opendistro-for-elasticsearch/anomaly-detection#132

[kaituo]

Proposal: delete checkpoints when stopping detector in terms of EndRunException (same as what we do when stopping a detector using RestFul API). When failing to delete a checkpoint, we should retry using exponential backoff.

StopDetectorTransportAction has logic on how to delete models.

anomaly-detection/src/main/java/org/opensearch/ad/AnomalyDetectorJobRunner.java

Line 516 in 553688a

private void stopAdJob(String detectorId, AnomalyDetectorFunction function) {

is the place you might want to add the delete model logic.

[minalsha]

@jackiehanyang what is the updated status of this issue? Is the fix in 2.8.0 ?