@Override
    public void run() {
      try {
        this.user.runAs(new PrivilegedAction<Object>() {
          @Override
          public Object run() {
            runRegionServer();
            return null;
          }
        });
      } catch (Throwable t) {
        LOG.error("Exception in run", t);
      } finally {
        // Run this on the way out.
        if (this.shutdownThread != null) {
          this.shutdownThread.start();
          Threads.shutdown(this.shutdownThread, 30000);
        }
      }
    }
List of RegionServers killed so far. ServerName also comprises startCode of a server, so any
restarted instances of the same server will have different ServerName and will not coincide
with past dead ones. So there's no need to cleanup this list.
hbase-server/src/test/java/org/apache/hadoop/hbase/SingleProcessHBaseCluster.java