Add some notes and clarify some details:
- You don't *have* to specify an IP protocol: non-IP Ethertypes are
possible
- It is not possible to automatically create ports *without* the default
SG (nor will it ever be possible - proxy APIs are bad)
- Remove the default SG can break access to the metadata service
Change-Id: Id66a92bdfd6e1663acddca830b2a9e99ac23a758
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>