Fixing validation for `create-policy`

The command validation for `create-policy` was not allowing the properties `enabled` and `max_count` to be included, even though the documentation includes them.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-203
Delete unpacked iso on repo deletion

When issuing the `delete-repo` command, the unpacked repo was being left on the filesystem. This change cleans up this folder, if it exists.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-202