Bug 841286

+++ This bug was initially created as a clone of Bug #841150 +++

Description of problem:
It's really inconvenient for the users each time to see the exhausted subscription in the list of available subscriptions list when they want to update/create an activation key with available subscription.

Version-Release number of selected component (if applicable):
pulp-common-1.1.11-1.el6.noarch
katello-certs-tools-1.1.6-1.git.572.1606589.el6.noarch
qpid-cpp-server-ssl-0.14-14.el6_2.x86_64
katello-glue-pulp-0.2.45-1.git.20.0d974f6.el6.noarch
katello-0.2.45-1.git.20.0d974f6.el6.noarch
katello-configure-0.2.30-1.git.16.0e273d4.el6.noarch
candlepin-tomcat6-0.5.32-1.el6.noarch
katello-qpid-client-key-pair-1.0-1.noarch
katello-cli-common-0.2.43-1.git.0.07c77a6.el6.noarch
katello-cli-0.2.43-1.git.0.07c77a6.el6.noarch
m2crypto-0.21.1.pulp-7.el6.x86_64
mod_wsgi-3.3-3.pulp.el6.x86_64
qpid-cpp-client-ssl-0.14-14.el6_2.x86_64
katello-glue-foreman-0.2.45-1.git.20.0d974f6.el6.noarch
katello-selinux-0.2.6-1.git.9.1606589.el6.noarch
katello-qpid-broker-key-pair-1.0-1.noarch
katello-agent-1.0.4-1.git.11.1606589.el6.noarch
python-qpid-0.14-7.el6_2.noarch
qpid-cpp-server-0.14-14.el6_2.x86_64
katello-glue-candlepin-0.2.45-1.git.20.0d974f6.el6.noarch
pulp-1.1.11-1.el6.noarch
katello-candlepin-cert-key-pair-1.0-1.noarch
python-oauth2-1.5.170-2.pulp.el6.noarch
candlepin-0.5.32-1.el6.noarch
qpid-cpp-client-0.14-14.el6_2.x86_64
katello-common-0.2.45-1.git.20.0d974f6.el6.noarch
katello-repos-0.2.5-1.el6.noarch
pulp-selinux-server-1.1.11-1.el6.noarch

How reproducible:
always.

Steps to Reproduce:
1.import manifest that has at least two diff. subscriptions.
2.register/subscribe clients as much to get the first subscription exhausted (all slots available subscribed). One can use subscription-manager register; subscription-manager subscribe; subscription-manager clean in a loop (clean will cleanup on system side but will keep subscription busy on Katello side)
3.now try to prepare a new AK and go to the UI tab for it, like: "https://<FQDN>/katello/activation_keys#panel=activation_key_<ID>&panelpage=available_subscriptions" - Available Subscriptions.
  
Actual results:
One can see the exhausted subscription too. But actually that subscription in _NOT_ available right now to be used.

Expected results:
each time retrieve from candlepin list of subscriptions that have free slots (as available to be consumed)

Additional info:
NOTE: if there would be a manual cleanup or unsubscribe that there would become an available slot from that subscription pool too - it _should_ start to be listed as available again!