Add new section "Log delivery" in CONTRIBUTING.rst
Add new section "Log delivery" in CONTRIBUTING.rst

Since Fluentd introduction in place of Heka the "Log delivery"
section must be adapted.

Change-Id: I734fd44ffc2fc0b43217542d3078dba0dff15539

dardelean/kolla-ansible,dardelean/kolla-ansible,dardelean/kolla-ansible