New rules for payment paths:

* Sanity check on newly created strands
* Better loop detection
* Better tests (test every combination of path element pairs)
* Disallow any root issuer (even for xrp)
* Disallow compount element typs in path
* Issue was not reset when currency was XRP
* Add amendment

src/test/app/Discrepancy_test.cpp

@@ -24,6 +24,7 @@
 #include <ripple/beast/unit_test.h>
 #include <ripple/beast/core/LexicalCast.h>
 #include <ripple/protocol/JsonFields.h>
+#include <ripple/protocol/Feature.h>
 #include <ripple/protocol/SField.h>
 
 namespace ripple {
@@ -36,11 +37,11 @@ class Discrepancy_test : public beast::unit_test::suite
     // A payment with path and sendmax is made and the transaction is queried
     // to verify that the net of balance changes match the fee charged.
     void
-    testXRPDiscrepancy ()
+    testXRPDiscrepancy (std::initializer_list<uint256> fs)
     {
         testcase ("Discrepancy test : XRP Discrepancy");
         using namespace test::jtx;
-        Env env {*this};
+        Env env {*this, features(fs)};
 
         Account A1 {"A1"};
         Account A2 {"A2"};
@@ -143,7 +144,9 @@ class Discrepancy_test : public beast::unit_test::suite
 public:
     void run ()
     {
-        testXRPDiscrepancy ();
+        testXRPDiscrepancy ({});
+        testXRPDiscrepancy ({featureFlow});
+        testXRPDiscrepancy ({featureFlow, featureToStrandV2});
     }
 };