refactor: CTransaction equality should consider witness data

It is not at all obvious that two transactions with differing witness data
should test equal to each other.

There was only a single instance of a caller relying on this behavior, and that
one appears accidental (left-over from before segwit). That caller (in the
wallet) has been fixed.

Change the definition of transaction equality (and inequality) to use the wtxid
instead.

src/primitives/transaction.h

@@ -360,12 +360,12 @@ public:
 
     friend bool operator==(const CTransaction& a, const CTransaction& b)
     {
-        return a.hash == b.hash;
+        return a.GetWitnessHash() == b.GetWitnessHash();
     }
 
     friend bool operator!=(const CTransaction& a, const CTransaction& b)
     {
-        return a.hash != b.hash;
+        return !operator==(a, b);
     }
 
     std::string ToString() const;