fix broken check of task success flag

The line in step-07 playbook,
    when_failed: $result
was not working with ansible 1.3.

Updated this to use the "when:" keyword for defining conditional
execution of a task
typo
fixed broken check of task failure

Replaced
        when_failed:$result
with
        when:result|failed
Merge pull request #17 from algal/master

Fix conditional execution on task success