fix idempotency for subscription pool id
fix idempotency for subscription pool id

subscription attach pool fails with subscription_pool_id
when it is already attached to the pool. Indeed the command:

   subscription-manager attach --pool=POOL

outputs a warning and return code is 1 when already attached.

This commit adds a check before trying to attach.

Change-Id: I05973a7e5851d3dd76361ac379c06c208e031e8d

redhat-cip/rcip-openshift-ansible,redhat-cip/rcip-openshift-ansible