Fix for subscribing non-custodial T1 data to DISK endpoint, issue #5066

removing all WMAgent oversight from the subscriptions

removing backup stuff

getting phedex nodes from the subscription as per discussion in pull request #5142

restoring behaviour of allowing phedex node to be determined from CMS site name but also allow specification of phedex node directly with no manipulation from the Agent

incorperating patch fixes from Dirk

disallowing assigning to Buffer PhEDEx node type
Merge pull request #5142 from alexanderrichards/disk_subscription

Disk subscription