aaa: display principal name post authn

post authn there is no sense to display the user that user entered, as
the principal name that is used is completely different.

Topic: AAA
Change-Id: Ibb0f7dd07d71cbcfc361f9da3d5ad677c5fb090b
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>