Revert "use SASL_USERNAME instead of its upstream value"

This reverts commit b4da9f55ee0010f516212393f5d0562c59603bd3.

Change-Id: Icfe7c7338d3c5cb4e17b9b94ea4fa441c9895e71
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/35801