@InterfaceAudience.Private
  public boolean waitForMetaOnline() {
    return isRegionOnline(RegionInfoBuilder.FIRST_META_REGIONINFO);
  }
Check hbase:meta is up and ready for reading. For use during Master startup only.
@return True if meta is UP and online and startup can progress. Otherwise, meta is not online
        and we will hold here until operator intervention.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java