public ServerName setRegionLocation(final ServerName serverName) {
    ServerName lastRegionLocation = this.regionLocation;
    if (LOG.isTraceEnabled() && serverName == null) {
      LOG.trace("Tracking when we are set to null " + this, new Throwable("TRACE"));
    }
    this.regionLocation = serverName;
    this.lastUpdate = EnvironmentEdgeManager.currentTime();
    return lastRegionLocation;
  }
Return whether the region has been split and not online.
<p/>
In this method we will test both region info and state, and will return true if either of the
test returns true. Please see the comments in
{@link AssignmentManager#markRegionAsSplit(RegionInfo, ServerName, RegionInfo, RegionInfo)} for
more details on why we need to test two conditions.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/RegionStateNode.java