Retrieve fluentd logs in gates

Fluentd send logs to stdout,
this changes creates a file with fluentd logs
output to easy discover missing patterns during fluentd
changes.

Change-Id: I131f95089eac60ccb4c48cf5071c3b44c5ea42ca

tests/get_logs.sh

@@ -45,6 +45,10 @@ copy_logs() {
         docker exec ceph_mon ceph osd tree > ${LOG_DIR}/kolla/ceph/ceph_osd_tree.txt
     fi
 
+    # container logs
+    mkdir ${LOG_DIR}/kolla/fluentd/
+    docker logs fluentd > ${LOG_DIR}/kolla/fluentd/fluentd.txt
+
     # Rename files to .txt; this is so that when displayed via
     # logs.openstack.org clicking results in the browser shows the
     # files, rather than trying to send it to another app or make you