When tmnxUserActionUnlock is set to 'doAction',
the user specified in tmnxUserActionUserName can make again
tmnxPasswordAttemptsCount unsuccessful login attempts
before he is locked out for tmnxPasswordAttemptsLockoutPeriod minutes,
and his exponential backoff period is reset to 1 second
if slcLoginExponentialBackOff is set to 'true'.
The value of tmnxUserActionUserName must be set
to a non-empty string in the same SNMP SET PDU when setting
tmnxUserActionUnlock to 'doAction'.