rpc: update graph topology related RPC's to recent db API change
rpc: update graph topology related RPC's to recent db API change

This commit updates all the RPC’s that deal with querying for data
stored within the graph to the latest version of the public API for the
graph itself.

LightningNetwork/lnd,aakselrod/lnd,AndrewSamokhvalov/lnd,LightningNetwork/lnd,AndrewSamokhvalov/lnd,ddustin/lnd,ddustin/lnd,aakselrod/lnd