lxd/container/lxc: Reorders containerLXC Delete() stages
lxd/container/lxc: Reorders containerLXC Delete() stages

As follows:

1. Storage volume removal (using new or old storage layer). Detects not found error for storage volume and skips.
2. If not snapshot: Remove backups, remove MAAS record, remove devices.
3. Remove Instance DB record.
4. Send lifecycle event.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

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