Be a bit more verbose during -loadblock if we already have blocks

src/main.cpp

@@ -3142,6 +3142,8 @@ bool LoadExternalBlockFile(FILE* fileIn, CDiskBlockPos *dbp)
                         nLoaded++;
                     if (state.IsError())
                         break;
+                } else if (hash != Params().HashGenesisBlock() && mapBlockIndex[hash]->nHeight % 1000 == 0) {
+                    LogPrintf("Block Import: already had block %s at height %d\n", hash.ToString(), mapBlockIndex[hash]->nHeight);
                 }
 
                 // Recursively process earlier encountered successors of this block