un-suppress the pylint error check for attribute_defined_outside_init,
and update the code to fix that error
Test Plan:
PASS: tox -e cover
PASS: system host-show controller-0
Story: 2008943
Task: 44051
Signed-off-by: Jia Hu <jia.hu@windriver.com>
Change-Id: I653c3f450eec96b84fa0e661350d308d4d2fdac6