Addition to Install docs for Satellite behind a proxy

I ran into the issue where we're behind a proxy and have selinux locking things down. We recieved the access denied error when we were expanding the Repository products:

Permission denied – connect(2) for “” port

To fix, I used the line from https://access.redhat.com/solutions/1308183 :

semanage port -a -t foreman_proxy_port_t -p tcp 

Since the semanage of ports was mentioned earlier in the document, this may be a big help to anybody else behind it who runs into the error to save them from having to hunt it down.