Description of problem:
We are using a proxy to download all content from the internet. 
The proxy is configured by the satellite-installer using the --katello-proxy-url option.
This works correctly for all parts except the pulp_streamer processes. Even the pulp metadata download worked with the proxy settings.
But when it comes to download an RPM file on the client.

https://li-lc-1578.hag.hilti.com/pulp/repos/Hilti/Library/hg-crash/content/dist/rhel/server/6/6.8/x86_64/os/redhat-release-server-6Server-6.8.0.5.el6.x86_64.rpm: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 503 Service Unavailable"


On the pulp server with streamer we see:

Jun 28 13:30:41 li-lc-1578 pulp_streamer: nectar.downloaders.threaded:DEBUG: Attempting to connect to https://cdn.redhat.com/content/dist/rhel/server/6/6.8/x86_64/os/Packages/redhat-release-server-6Server-6.8.0.5.el6.x86_64.rpm.
Jun 28 13:30:41 li-lc-1578 pulp_streamer: requests.packages.urllib3.connectionpool:INFO: Starting new HTTPS connection (2): cdn.redhat.com
Jun 28 13:30:47 li-lc-1578 pulp_streamer: nectar.downloaders.threaded:ERROR: Skipping requests to cdn.redhat.com due to repeated connection failures: HTTPSConnectionPool(host='cdn.redhat.com', port=443): Max retries exceeded with url: /content/dist/rhel/server/6/6.8/x86_64/os/Packages/redhat-release-server-6Server-6.8.0.5.el6.x86_64.rpm (Caused by ConnectTimeoutError(<requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x36a68d0>, 'Connection to cdn.redhat.com timed out. (connect timeout=6.05)'))
Jun 28 13:30:47 li-lc-1578 pulp_streamer: [-] 127.0.0.1 - - [28/Jun/2016:13:30:46 +0000] "GET /var/lib/pulp/content/units/rpm/de/4659f4f8037b876ca7fc0b45b614289f28f8985bccaa64b8c037e065e6d19a/redhat-release-server-6Server-6.8.0.5.el6.x86_64.rpm HTTP/1.1" 503 - "-" "urlgrabber/3.9.1 yum/3.2.29"

On our upstream proxy, there is no request to cdn.redhat.com visible. This makes me believe that the proxy configuration is not used by pulp_streamer.
Doing a grep for proxy configuration in /etc/pulp shows that the pulp_streamer has no proxy configuration defined:

[crash] root@li-lc-1578:/etc/pulp# grep -Rl proxy
server/plugins.conf.d/docker_importer.json
server/plugins.conf.d/yum_importer.json
server/plugins.conf.d/puppet_importer.json
server/plugins.conf.d/iso_importer.json
server.conf



Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. Use external proxy to connect to CDN, makes sure to not allow direct internet access from the satellite
2. Create clean satellite with the --katello-proxy-url option to the the external proxy
2. Enable on_demand in settings, this must be before any repo is created to have it set as default
3. Sync RedHat manifest
4. Select some RedHat repos to sync
5. Create content view and activation key
6. Assign RedHat repos to a content hosts
7. yum repolist
8. yum update (or install, just make sure a package will be downlaoded)

Actual results:
Step 7 repolist works
Step 8 package download fails

Expected results:
Success

Additional info: