Comment 4 for bug 1449318

It seems this is fixable by setting KillMode=process
See http://www.freedesktop.org/software/systemd/man/systemd.kill.html

$ bzr diff
=== modified file 'systemd/cloud-final.service'
--- systemd/cloud-final.service 2015-04-09 15:54:01 +0000
+++ systemd/cloud-final.service 2015-11-30 20:17:47 +0000
@@ -8,6 +8,7 @@
 ExecStart=/usr/bin/cloud-init modules --mode=final
 RemainAfterExit=yes
 TimeoutSec=0
+KillMode=process

 # Output needs to appear in instance console output
 StandardOutput=journal+console