Move flavor definition closer together

Just make it easier to read, really.
Set s3_url to the nova api host

This one always runs nova objectstore
Fix reading of EC2 credentials

without terminating the list of options to grep the regexp
is treated as an option - which gives the error message "no such option"
Switch to using KeystoneSettings

KeystoneSettings also provides the ability to transparently
handle SSL support in the future.
Always use action :nothing

We already run it in the initial phase of chef,
no need to run it twice.
Fix creation of EC2 credentials

The keystone_register interface was apparently changed
inbetween. Adjust to the new way of calling it.
Pass down keystone_settings to the template

Also sort options to make it easier to get an
overview.