added comments for tabula callbacks
added comments for tabula callbacks

couchbaselabs/priority15,couchbaselabs/priority15,couchbase/cbmonitor,mikewied/cbagent,couchbaselabs/litmus,vmx/cbagent,couchbase/cbagent,couchbaselabs/litmus,couchbase/cbmonitor,ronniedada/litmus,couchbaselabs/litmus,ronniedada/litmus,pavel-paulau/cbagent,couchbaselabs/priority15