Merge #700: [0.17] sendtomainchain pak fix

ef64be6 fix HelpExamplRPC port for liquidv1 vs bitcoin mainnet (Gregory Sanders)
db01a6d Fix sendtomainchain with pak when subtracting fee from output (Gregory Sanders)

Pull request description:

  regression introduced in 0.17 catchup with the convergence of liquid and elements codebases.

Tree-SHA512: 6b3c4d2fbb212180818b4dd86eb4a29913ac7d4ea18bb603d851e6a9966480f46539d1ed79b8637a77101cac6fa6e98483c4b0d21dc665c2f8ab3cc6a25b4b04

src/rpc/server.cpp

@@ -520,7 +520,7 @@ std::string HelpExampleCli(const std::string& methodname, const std::string& arg
 std::string HelpExampleRpc(const std::string& methodname, const std::string& args)
 {
     return "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\":\"curltest\", "
-        "\"method\": \"" + methodname + "\", \"params\": [" + args + "] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n";
+        "\"method\": \"" + methodname + "\", \"params\": [" + args + "] }' -H 'content-type: text/plain;' http://127.0.0.1:7041/\n";
 }
 
 void RPCSetTimerInterfaceIfUnset(RPCTimerInterface *iface)

src/wallet/rpcwallet.cpp

@@ -4864,7 +4864,7 @@ UniValue sendtomainchain_pak(const JSONRPCRequest& request)
 
     bool subtract_fee = false;
     if (request.params.size() > 2) {
-        subtract_fee = request.params[1].get_bool();
+        subtract_fee = request.params[2].get_bool();
     }
 
     CPAKList paklist = g_paklist_blockchain;

test/functional/feature_pak.py

@@ -408,6 +408,10 @@ def compare(actual, expected):
                     raise Exception("Found unexpected peg-out output")
         assert(peg_out_found)
 
+        # Test that subtracting fee from output works
+        self.nodes[i_pak1].sendtomainchain("", self.nodes[i_pak1].getbalance()["bitcoin"], True)
+        assert_equal(self.nodes[i_pak1].getbalance()["bitcoin"], 0)
+
         # TODO: create rawsendtomainchain to do transaction surgery for testing
 
 if __name__ == '__main__':