Removing /dev/log on rsyslog start

Currently we seem to be experiencing races between containers.
If another containers tries to write to rsyslog before rsyslog container
is up and running it will create /dev/log as directory,
and that will prevent rsyslog from starting.

Change-Id: I88ac27693d12e605f95e3a945fc98783516d7933
Closes-Bug: #1501694
backport: liberty

docker/logging/rsyslog/Dockerfile.j2

@@ -13,4 +13,6 @@ RUN apt-get install -y --no-install-recommends rsyslog \
 
 {% endif %}
 
+COPY extend_start.sh /usr/local/bin/kolla_extend_start
+
 {{ include_footer }}

docker/logging/rsyslog/extend_start.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+if [[ -e "/dev/log" ]]; then
+    rm -rf /dev/log
+fi