@Override
  public void close() throws KerberosOperationException {

    if (credentialsCacheFile != null) {
      if (credentialsCacheFile.delete()) {
        LOG.debug("Failed to remove the cache file, {}", credentialsCacheFile.getAbsolutePath());
      }
      credentialsCacheFile = null;
    }

    environmentMap = null;
    executableKinit = null;
    cachedKeytabs = null;
    adminServerHost = null;
    adminServerHostAndPort = null;

    super.close();
  }
A Map of environmet values to send to system command invocations.
<p>
This map is to be appened to any map of environment values passed in when
invoking {@link KerberosOperationHandler#executeCommand(String[], Map, ShellCommandUtil.InteractiveHandler)}
ambari-server/src/main/java/org/apache/ambari/server/serveraction/kerberos/KDCKerberosOperationHandler.java