Add the storage_policy attribute to the metadata returned
when listing containers using the GET account API function.
The storage policy of a container is a very useful attribute
for telemetry and billing purposes, as it determines the location
and method/redundancy of on-disk storage for the objects in the
container. Ceilometer currently cannot define the storage policy as a
metadata attribute in Gnocchi as GET account, the most efficient way
of discovering all containers in an account, does not return the
storage policy for each container.
Returning the storage policy for each container in GET account
is the ideal way of resolving this issue, as it allows Ceilometer
to find all containers' storage policies without performing additional
costly API calls.
Special care has been taken to ensure the change is backwards
compatible when migrating from pre-storage policy versions
of Swift, even though those versions are quite old now.
This special handling can be removed if support for migrating
from older versions is discontinued.
Closes-bug: #2097074
Change-Id: I52b37cfa49cac8675f5087bcbcfe18db0b46d887
965cc2fcbc