multi: fix newly detected linter issues

contractcourt/htlc_success_resolver.go

@@ -515,8 +515,8 @@ func (h *htlcSuccessResolver) report() *ContractReport {
 
 	h.reportLock.Lock()
 	defer h.reportLock.Unlock()
-	copy := h.currentReport
-	return &copy
+	cpy := h.currentReport
+	return &cpy
 }
 
 func (h *htlcSuccessResolver) initReport() {