Add fullyNotified to getblockchaininfo and use it in tests

src/rpc/blockchain.cpp

@@ -1335,6 +1335,12 @@ UniValue getblockchaininfo(const UniValue& params, bool fHelp, const CPubKey& my
 
         obj.push_back(Pair("pruneheight",        block->GetHeight()));
     }
+
+    // this helps our tests work correctly
+    if (Params().NetworkIDString() == "regtest") {
+        obj.pushKV("fullyNotified", ChainIsFullyNotified());
+    }
+
     return obj;
 }