void addSource(String srcName, VertexState sourceState) {
      sourcesOfInterest.put(srcName, sourceState);
    }
Constructs FragmentRuntimeInfo for scheduling within LLAP daemons.
Also caches state based on state updates.
@param vertexName
@param fragmentNumber
@param priority
@return
llap-tez/src/java/org/apache/hadoop/hive/llap/tezplugins/helpers/SourceStateTracker.java