query container location

jclouds allows creating a container in a specified location but does not allow querying the location of a container afterwards.  At least two providers directly support this, a third likely supports it indirectly, and others could provide the account-level region:

• AWS S3 supported
• Azure unsupported, but could return account-level region
• Backblaze B2 unsupported, but could return the single region it provides
• Google Cloud Storage supported
• OpenStack Swift likely supported by storage policies, needs investigation
• filesystem blobstore could attach some metadata to the directory via extended attributes