Handle the hardcoded configuration values

This patch allows to customize the hardcoded configuration values,
as well as introduce new configuration options for aodh services
by configmap template with the specified section:

  aodh:
    server:
      configmap:
        DEFAULT:
          rest_notifier_max_retries: 0
          notifier_topic: alarming
        api:
          user_alarm_quota: 10
          project_alarm_quota: 10
          alarm_max_actions: -1

Change-Id: I49fe8402d99b1cefb58e3449137df255924d3f2b
Related-Prod: PROD-29627
7 files changed