spice: more flexibility in binding options

Allow to use a different binding between nova services and spice.
The use case is that Spice is not working well yet with SSL.
With this patch, you are now able to use SSL for all services except
Spice.

Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge pull request #522 from enovance/spice-flexibility

spice: more flexibility in binding options