code: public boolean validateMigrationStamp(int stamp) {
          int completed = ownerMigrationsCompleted.get();
          int started = ownerMigrationsStarted.get();
          return stamp == completed && stamp == started;
      }
docs: Returns true if there's no primary replica migrations started and/or completed
  since issuance of the given stamp. Otherwise returns false, if there's an ongoing migration
  when stamp is issued or a new migration is started (and optionally completed) after stamp is issued.
  
  @param stamp a stamp
  @return true stamp is valid since issuance of the given stamp, false otherwise