Possible bug when using serial and run_once

Hello Group,

Here is another possible bug. When using serial and run_once, the run_once command is executed for every serial-loop, instead of once for the entire playbook. I expected it to run only once for the entire playbook.

I'm using the latest ansible 1.8.2

Here is an example: I expect the shell: true command to run only once for the entire playbook.

$ cat bug2.yml