Prevent user from specifying conflicting parameters to fundrawtx

estimate_mode/conf_target both are overridden by feeRate, so should
not be specified together with feeRate.

src/wallet/rpcwallet.cpp

@@ -2795,9 +2795,15 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
             coinControl.signalRbf = options["replaceable"].get_bool();
         }
         if (options.exists("conf_target")) {
+            if (options.exists("feeRate")) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both conf_target and feeRate");
+            }
             coinControl.m_confirm_target = ParseConfirmTarget(options["conf_target"]);
         }
         if (options.exists("estimate_mode")) {
+            if (options.exists("feeRate")) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both estimate_mode and feeRate");
+            }
             if (!FeeModeFromString(options["estimate_mode"].get_str(), coinControl.m_fee_mode)) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid estimate_mode parameter");
             }