launch: stream syslog on remote host

So that operators have a clue what's going on during the long
initial puppet run.

Change-Id: If310c3420d942c79c8b04d3e9ce68f39081cc507

launch/launch-node.py

@@ -23,6 +23,7 @@ import os
 import shutil
 import subprocess
 import sys
+import threading
 import tempfile
 import time
 import traceback
@@ -85,6 +86,13 @@ def run(cmd, **args):
     return ret
 
 
+def stream_syslog(ssh_client):
+    try:
+        ssh_client.ssh('tail -f /var/log/syslog')
+    except Exception:
+        print "Syslog stream terminated"
+
+
 def bootstrap_server(server, key, name, volume_device, keep,
                      mount_path, fs_label):
 
@@ -179,6 +187,10 @@ def bootstrap_server(server, key, name, volume_device, keep,
         os.symlink('/etc/ansible/hosts/generated-groups',
                    jobdir.groups)
 
+        t = threading.Thread(target=stream_syslog, args=(ssh_client,))
+        t.daemon = True
+        t.start()
+
         ansible_cmd = [
             'ansible-playbook',
             '-i', jobdir.inventory_root, '-l', name,