Link kolla_log volume dir to /var/log/kolla

The path /var/lib/docker/volumes/kolla_logs/_data/ is too long
shorter log path will help to debug from log.
The volume path is compatible with docker-engine and docker-ce.

Change-Id: I9195d5f24d938f5060fe748aac3ae58c79ec5abf

ansible/roles/common/tasks/bootstrap.yml

@@ -5,3 +5,10 @@
     action: "create_volume"
     common_options: "{{ docker_common_options }}"
     name: "kolla_logs"
+
+- name: Link kolla_logs volume to /var/log/kolla
+  become: true
+  file:
+    src: /var/lib/docker/volumes/kolla_logs/_data
+    path: /var/log/kolla
+    state: link

doc/source/user/troubleshooting.rst

@@ -95,6 +95,14 @@ provide no information.
 To learn more about Docker command line operation please refer to `Docker
 documentation <https://docs.docker.com/reference/>`__.
 
+The log volume "kolla_logs" is linked to ``/var/log/kolla`` on the host.
+You can find all kolla logs in there.
+
+.. code-block:: console
+
+   readlink -f /var/log/kolla
+   /var/lib/docker/volumes/kolla_logs/_data
+
 When ``enable_central_logging`` is enabled, to view the logs in a web browser
 using Kibana, go to
 ``http://<kolla_internal_vip_address>:<kibana_server_port>`` or

releasenotes/notes/link_kolla_logs-e57a1e583f2872eb.yaml

+---
+other:
+  - |
+    Link kolla_logs docker volume to /var/log/kolla.
+    Shorter log path will help to debug from log.
+    The volume path is compatible with docker-engine and docker-ce.

tools/cleanup-containers

@@ -43,4 +43,7 @@ done
 echo "Removing volumes..."
 (docker volume rm ${volumes_to_remove} 2>&1) > /dev/null
 
+echo "Removing link of kolla_log volume..."
+(rm -f /var/log/kolla 2>&1) > /dev/null
+
 echo "All cleaned up!"