credentialRepresentation.setTemporary(true); IS IGNORE

#1 
    CredentialRepresentation credentialRepresentation = new CredentialRepresentation();
    credentialRepresentation.setValue(CredentialRepresentation.PASSWORD);
    credentialRepresentation.setValue(tempPassword);
    credentialRepresentation.setTemporary(true)
#2

If you can give us a little more information on how you are using this, we can try to help you debug. Is it in a custom Authenticator? REST endpoint? Admin API?