Da Risk <da_risk@beem-project.com> [Wed, 06 Mar 2013 21:30:51 +0100] rev 1027
Scram-Sha-1 mechanism : do not send authzid if it not absolutely necessary
Some servers (ejabberd) reject the challenge if the
scram attributes a (authzid) and n (authcid) are equals
or they just don't handle the authzid.
So we just don't send it if they are the same
This fix #484