Fix copy on write for amount_t::in_place_roundto

- Copy amount quantity before rounding.
- Fix `amount_t::roundto(int)`.
- Transform `balance/testRound` into `balance/testRoundto`.
  It was a mix of `round` and `roundto` operation with unclear purpose
  and was relying on `in_place_roundto` behavior modifying all copies.

There is no unit tests for balance `round` and `unround` any more.

Closes #2362

1 files changed, 1 insertions, 1 deletions

diff --git a/src/amount.h b/src/amount.h
index 7abaa1c9..5638abc9 100644
--- a/src/amount.h
+++ b/src/amount.h
@@ -347,7 +347,7 @@ public:
 
   amount_t roundto(int places) const {
     amount_t temp(*this);
-    temp.in_place_round();
+    temp.in_place_roundto(places);
     return temp;
   }
   void in_place_roundto(int places);