Fixes #7636: Add Katello Disconnected user guide.

these steps don't actually work as is, because some of the pulp services above won't start if the db hasn't been migrated.  I'd recommend just copying from https://access.redhat.com/documentation/en-US/Red_Hat_Satellite/6.0/html/User_Guide/sect-Disconnected_Satellite.html#Configuring_the_Synchronization_Host  (step 11)