Added `enable_repos` function to ui/activationkey module.

This function helps us to enable particular repos,
which by default are disabled.

Changing default settings for content hosts that register with
this activation key requires subscription-manager version 1.10
or newer to be installed on that host.

For rhel65 the installed version is 1.9 on the clients, hence
Enabling the repo via the UI doesn't enabled the repo.

Also enabling repos uses the sub-man instead of yum-config-manager.
Merge pull request #1761 from kbidarkar/add-ak-enable_repos

Added `enable_repos` function to ui/activationkey module.
Make rhel_content_org a brand new org
This change gives me 0 errors in test_contentviews
Removed the caching from TestContentView.env1 to fix "Prior environment can only
 have one child" error.
Merge pull request #1765 from JacobCallahan/master

Make rhel_content_org a brand new org