Disable and Enable repos every run

[tahonen]

To make stc run more solid we should disable and enable repos in every run. This way users can subscribe hosts before validation run.

[rbo]

I removed the repo enabling with Issuer #74 and replace the subscription check with a pure check, nothing is changed.
If you like to subscripte / enable repos there some helper playbooks:

• Subscriptions are allocated to systems (machines).
• Incase it is not, we provide an helper playbook:

    ./setup.sh
    cp playbooks/subscription-register.yml playbooks/subscription-register-private.yml

    $EDITOR playbooks/subscription-register-private.yml <1>
    ansible-playbook -i inventory playbooks/subscription-register-private.yml

<1> Adjust playbook - add RHSN user, passwort or activation key & org and pool id

• Repositories enabled (The subscription-register* playbook above add repositories to )

Does the behavior fit?