Delegate FTP publisher to 127.0.0.1

We want ansible to run lftp on our zuul-launcher servers, not our
remote nodes.

Change-Id: I0ec9182ce431c9421df8633717f78fc0d3b683f3
Signed-off-by: Paul Belanger <pabelanger@redhat.com>
diff --git a/zuul/launcher/ansiblelaunchserver.py b/zuul/launcher/ansiblelaunchserver.py
index 5bef6d3..dbce8bf 100644
--- a/zuul/launcher/ansiblelaunchserver.py
+++ b/zuul/launcher/ansiblelaunchserver.py
@@ -927,7 +927,8 @@
                     when='success')
         tasks.append(task)
         task = dict(shell='lftp -f %s' % ftpscript,
-                    when='success')
+                    when='success',
+                    delegate_to='127.0.0.1')
         ftpsource = ftpcontent
         if ftp.get('remove-prefix'):
             ftpsource = os.path.join(ftpcontent, ftp['remove-prefix'])