Fix cloud-init clean for trusty

   * Trusty cloud-init pkg don't have 'clean' option

Change-Id: I24292571e60c3e149adaff99b4a23c847d56f79a
diff --git a/common/ubuntu_cleanup.sh b/common/ubuntu_cleanup.sh
index 686e95e..ba69e3c 100644
--- a/common/ubuntu_cleanup.sh
+++ b/common/ubuntu_cleanup.sh
@@ -37,7 +37,7 @@
 # Force cleanup cloud-init data, if it was
 if [[ -d '/var/lib/cloud/' ]] ; then
   rm -rf /var/lib/cloud/* || true
-  cloud-init clean
+  cloud-init clean || true
   echo > /var/log/cloud-init-output.log || true
   echo > /var/log/cloud-init.log || true
 fi