protected int getNumBlobsErased(CloudStorageCompactor compactor) {
    // Timed wait is better than an indefinite one
    int wait = 30;
    if (!compactor.isCompactionDone(wait)) {
      fail(String.format("Main compaction thread did not finish in %s seconds", wait));
    }
    return compactor.getNumBlobsErased();
  }
Waits for main compaction thread to end and return num of blob erased
@param compactor
ambry-cloud/src/test/java/com/github/ambry/cloud/CloudStorageCompactorTest.java