task.ansible: Allow passing in custom group_vars

task.ansible: Allow passing in custom group_vars

Up until now, if you wanted to inject vars to a playbook run, you had to
use --extra-vars, which don't behave the same way that group_vars do.
This commit adds that functionality.

We look for a 'group_vars' dict in the task's config object. If it's
there, we create group_vars files with names taken from the keys, and
content taken from the values.

Signed-off-by: Zack Cerza <zack@redhat.com>