This prevents annoying task errors (even though they are ignored)
when testing on non-Arch distributions.
Running the "prepare" command, this was always visible:
> fatal: [instance]: FAILED! => {"changed": false, "msg": "Failed to find required executable \"pacman\" in paths: /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin"}
Signed-off-by: René Scheibe <rene.scheibe@gmail.com>
