Add tagging button for cloud object store containers.

[martinpovolny]

Fix "Tag" button for Object store container.

https://bugzilla.redhat.com/show_bug.cgi?id=1494344

Steps to Reproduce:

1. Add cloud provider first (Openstack RHOS7-GA recommended)
2. Navigate to Compute -> Cloud -> Tenants
3. Click on 'admin' from 'Cloud Tenants' table
4. Click on 'Cloud Object Store Containers' from 'Relationship' table
5. Click on one 'Cloud Object Store Containers' from 'All Images' table
6. From 'Policy' select 'Edit tag'

ping @tzumainn, @petrblaho, @aufi : please, review.

[miq-bot]

Checked commit martinpovolny@ae3e02f with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
1 file checked, 0 offenses detected
Everything looks fine. 👍

[aufi]

I believe, that Cloud Object Store belongs to Storage provider (main repo), which is mostly handled by @roliveri team. But from my point of view, looks good to me.