An interesting new feature of Caching Server 5 is the ability to cache personal iCloud data.  There could be a variety of reasons why this may not be desirable in some environments, one of which could be concerns over storage capacity on the caching server.  Here is how to disable that feature using the serveradmin command in Terminal:

sudo serveradmin settings caching:AllowPersonalCaching = no

Change that boolean field to yes to re-enable this feature.