The value of tmnxKeyChainKeyEndTime specifies the calendar date and
time after which the key specified by
tmnxKeyChainAuthenticationKey is no longer eligible to sign and/or
authenticate the protocol stream.
tmnxKeyChainKeyEndTime is not applicable when
tmnxKeyChainKeyDirection is set to 'send' or 'send-receive'.
If no date and time is set, tmnxKeyChainKeyEndTime is represented by
a DateAndTime string with all NULLs and the key is valid
indefinitely.