Changed pre-start script to create the DLQ dir

If the folder defined in the DLQ path does not exist, logstash will fail
to start.

We need to create it in the pre-start script to avoid having this issue.

jobs/logstash/templates/bin/pre-start

@@ -20,6 +20,11 @@ mkdir -p "$CONFD_DIR" && chmod 775 "$CONFD_DIR" && chown vcap.vcap "$CONFD_DIR"
 cd "${CONFD_DIR}"
 source /var/vcap/jobs/logstash/config/confd.sh
 
+# setup dead letter queues folder
+export DLQ_DIR="/var/vcap/store/logstash/plugins/inputs/dead_letter_queue"
+mkdir -p "$DLQ_DIR"
+chown vcap.vcap "$DLQ_DIR"
+
 # Install plugins
 <% p("logstash.plugins").each do |plugin| %>
 logstash-plugin install \