public boolean authThresholdReached() {
    if (allowedAuthAttempts < 0) {
      return false; // negative value means auth forever
    } else if (authAttempts >= allowedAuthAttempts) {
      return true;
    } else {
      authAttempts++;
      return false;
    }
  }
Get a typical auth descriptor for CRAM-MD5 or PLAIN auth with the given
username and password.

@param u the username
@param p the password

@return an AuthDescriptor
src/main/java/net/spy/memcached/auth/AuthDescriptor.java