Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1710697

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"

1. 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