Refactor orders cleanup

This patch continues the refactor of cleanup logic.  It adds a
new `cleanup()` method to the order client that attempts to delete
all orders and all screts created by those orders on cleanup.

This patch also adds some scaffolding to the Container client that
will be fleshed out in a follow-up patch.

Change-Id: I78d875980637e82ddc3173aad2fc7ecf4941230c
4 files changed