Description of problem:
When we are generating inventory json/tarball, some hosts might have empty account field.


Version-Release number of selected component (if applicable):
satellite-6.7.0-6.el7sat.noarch
tfm-rubygem-foreman_inventory_upload-1.0.2-1.el7sat.noarch


How reproducible:
always


Steps to Reproduce:
1. Have a client that consumes two pools:
    # subscription-manager list --consumed | grep -e 'Subscription Name' -e 'Account'
    Subscription Name:   Red Hat Enterprise Linux Server, Standard (Physical or Virtual Nodes)
    Account:             1212729
    Subscription Name:   MyCustomProduct
    Account:             
2. When I generate and upload inventory in RH Inventory -> Manage -> Restart
   it passes
3. Now when I look into the json which was archived, account field is empty:
    # tar xzf /var/lib/foreman/red_hat_inventory/uploads/done/report_for_1.tar.gz
    # cat 5cd1e4a9-6b1d-43b6-bd81-aede6401f5a1.json | json_reformat | grep -e fqdn -e account


Actual results:
            "fqdn": "gprfc009-02.contperf66.local",
            "account": "",


Expected results:
            "fqdn": "gprfc009-02.contperf66.local",
            "account": "1212729",


Additional info:
When we have removed MyCustomProduct subscription (with `subscription-manager remove --pool=8a901f1d70ed75db0170ed91d93731b0`) from the host and restarted inventory generation, it worked as expected.