Trivial Description
TestAtomicOperation has a bunch of tests which spawn a bunch of tests that do puts, appends, deletes, inc and then does gets to make sure that things happened. It uses TEST_UTIL.getLocalHRegion() to obtain an HRegion object. So, in essence the test doesn't need to sync to disk to make sure the edits have persisted. There is no regionserver/master to take care of wal replay or any failure for that matter. So, converting all the Durability settings for the edits to ASYNC_WAL seems like the right thing to do here to make the test run faster.