Adapt sapling_wallet_listreceived.py to the new wtx confirmation structure.

The block index initial value is 0, not -1 now.

Author: furszy

test/functional/sapling_wallet_listreceived.py

@@ -95,7 +95,7 @@ def run_test(self):
         assert_false(r[0]['change'], "Note should not be change")
         assert_equal(my_memo_hex, r[0]['memo'])
         assert_equal(0, r[0]['confirmations'])
-        assert_equal(-1, r[0]['blockindex'])
+        assert_equal(0, r[0]['blockindex'])
         assert_equal(0, r[0]['blockheight'])
 
         c = self.nodes[1].getsaplingnotescount(0)