private void transitionToPendingAndClearList(List<Call> calls) {
            for (Call call : calls) {
                call.curNode = null;
                pendingCalls.add(call);
            }
            calls.clear();
        }
Add some calls to pendingCalls, and then clear the input list.
Also clears Call#curNode.

@param calls         The calls to add.
clients/src/main/java/org/apache/kafka/clients/admin/KafkaAdminClient.java