Improves unit test coverage for dcmanager's alarm_manager and notifications APIs
from 73% and 85%, respectively, to 100%.
Test plan:
All of the tests were created taking into account the
output of 'tox -c tox.ini -e cover' command
Story: 2007082
Task: 49317
Change-Id: I8fd1a60ded61ca5dc8edcd8f4297fca974ba1e24
Signed-off-by: rlima <Raphael.Lima@windriver.com>