aaa: Retrive values from domain using case insensitve name of the domain

This patch is aimed to solve case sensitivy issues for FreeIPA when
upgrading from 3.4 to 3.5

Change-Id: Ieeaf9c922d6d3f0b9bd2a4480859c4ce483454f9
Topic: AAA
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>