Expand viva_las_vegas tests

[PopovaPolina]

Expand viva_las_vegas tests:

• test command список заявок
• test command @username хочет в отпуск
• test command viva reset
• test daily reminder
• test reminders to inform customer before leaving
• test filtering of inactive users
• test resetting user status after coming back from vacation and if it is impossible to ask for the second leave request

Part of these tests cases is required for the implementation of issue #68 (for test cases where multiple users are in use).