The value of tmnxNtpAuthKeyType specifies the type of
authentication method used to authenticate and NTP packet.
des (1) - Use DES authentication
messageDigest (2) - Use MD5 authentication as specified
in RFC-2104.
A value must be set for tmnxNtpAuthKeyType in order for
tmnxNtpAuthKeyEntryStatus to successfully transition
to the 'active' state.