Store login failure error messages in the transaction
This will propogate messages up from failed form authentication
so they are correctly displayed in a SAML2 transaction for a
user with an expired password, for example.
The message is wiped after retrieval to ensure that a stale
message won't be displayed in the future.
https://fedorahosted.org/ipsilon/ticket/69
Signed-off-by: Rob Crittenden <rcritten@redhat.com>
Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>