puppet_runonce: redirect stderr to stdout (puppetlabs#523)

In case the Puppet Agent fails, it prints an error to stderr. Previously
when running the task, and the agent failed, it would output only normal
stdout, which contained only successful changes, and actual errors were
hidden.

tasks/puppet_runonce.sh

@@ -39,7 +39,7 @@ echo
   --detailed-exitcodes \
   --color false \
   $ENV_FLAG \
-  $NOOP_FLAG
+  $NOOP_FLAG 2>&1
 
 # Only exit non-zero if an error occurred. Changes (detailed exit code 2) are
 # not errors.