The placement config may eventually be shared among more than one
charm as more services begin to use it. This patch drops the local
sectional config and uses the same sectional config that now exists
in charm-helpers.
charm-helpers was synced to pick up this change.
Change-Id: I42b415d7c4834cd74887c27b2f4a4daeb8eae636
Related-Bug: 1850691