[Flaky Test] rollup test flaky because didn't assert job finish properly

[bowenlan-amzn]

Flaky symptom:

mapper [rollup_metadata.continuous.next_window_end_time] cannot be changed from type [long] to [date]

version conflict, required seqNo [7], primary term [1]. current document has seqNo [8] and primary term [1]","index":".opendistro-ism-config","shard":"3","index_uuid":"mqJmMNSZTA20CFiqJLw5Ag"

Rollup is not STARTED expected:<started> but was:<finished>

Refer to the analysis https://github.com/opensearch-project/index-management/issues/90#issuecomment-1370070482 which provides a clear path forward to fix such flaky scenario