identity: more flexibility in endpoints protocols

Allow to specify all endpoint type protocols:
- recatorize keystone endpoints
- for each OpenStack service, allow to specify internal & admin
  endpoints procotols

Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
endpoint protocols: flexibility in OpenStack services

Allow some OpenStack services to specify either HTTP or HTTPS to connect
each others.

Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge pull request #517 from enovance/https-endpoints

identity: more flexibility in endpoints protocols