Handle the hardcoded configuration values

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

    glance:
      server:
        configmap:
          glace_api:
            DEFAULT:
              image_member_quota = 128
              image_property_quota = 128
              image_tag_quota = 128
              image_location_quota = 10
              user_storage_quota = 0
          glace_registry:
            DEFAULT:
              image_member_quota = 128
              image_property_quota = 128
              image_tag_quota = 128
              image_location_quota = 10
              user_storage_quota = 0
          ...

Change-Id: Ie74a66321ec39d154cac95d3315381c395b5582c
Related-Prod: PROD-29040
19 files changed