Don't set krbLastPwdChange when setting a host OTP password.
    
    We have no visibility into whether an entry has a keytab or not so
    krbLastPwdChange is used as a rough guide.
    
    If this value exists during enrollment then it fails because the host
    is considered already joined. This was getting set when a OTP was
    added to a host that had already been enrolled (e.g. you enroll a host,
    unenroll it, set a OTP, then try to re-enroll). The second enrollment
    was failing because the enrollment plugin thought it was still
    enrolled becaused krbLastPwdChange was set.
    
    https://fedorahosted.org/freeipa/ticket/1357