[MFTF] User signs out from Stock

[filmaj]

Description

Implement MFTF test to cover scenario: "User signs out from Stock" (story 36, #389)

Preconditions

1. Admin User is logged into Admin Panel

Test steps

2. Open Adobe Stock Images Grid
3. User signs into Adobe IMS
4. Click on User's name in the top-right
5. Click on Sign Out button
6. Verify that User's name is not displayed and that Sign In button is displayed