Description of problem:

If user set a value for "http_proxy" and then unset it. Satellite will set the http_proxy to ''(empty string). This is causing all the outgoing http requests not using proxy including the outgoing traffic to Customer Portal. The katello "cdn_proxy" setting is ignored and Satellite will connect to the Customer Portal directly. Thus, manifest refresh fails.

In "/usr/share/foreman/lib/foreman/http_proxy.rb"

    # Answers if this request should be proxied
    def proxy_http_request?(current_proxy, request_host, schema)
      !http_proxy.nil? &&     <========== This is using ".nil?" which will return false for empty string. Suggest to use ".blank?" which should fix the issue.
      current_proxy.nil? &&
      !request_host.nil? &&
      http_request?(schema) &&
      http_proxy_host?(request_host) &&
      !local_request?(request_host)
    end


Steps to Reproduce:
1. http_proxy setting is nil in the beginning.

echo "select id,name,value from settings where name = 'http_proxy'" | su postgres -c 'psql foreman'
 id  |    name    | value 
-----+------------+-------
 108 | http_proxy |

2. Go to the Setting page set the http_proxy to any url, such as http://proxy.example.com and save it.

echo "select id,name,value from settings where name = 'http_proxy'" | su postgres -c 'psql foreman'
 id  |    name    |            value             
-----+------------+------------------------------
 108 | http_proxy | --- http://proxy.example.com+
     |            | ...

3. Still in the Setting page unset the http_proxy and save it.

echo "select name,value from settings where name = 'http_proxy'" | su postgres -c 'psql foreman'
    name    | value  
------------+--------
 http_proxy | --- ''

4. Block your Satellite to connect to the Customer portal directly.

5. Set the cdn_proxy in etc/foreman/plugins/katello.yaml

  :cdn_proxy:
    :host: http://proxy.example.com
    :port: 3128
    :user: hao
    :password: mypassword

6. Restart Satellite.

7. Refresh Manifest and the Foreman task should fail with connection error.

8. Check the production.log, you should see something like.

[app] [I] Proxying request to subscription.rhsm.redhat.com via