Ensure logout before doing login testing (needed for session sharing)

Signed-off-by: Michal Čihař <michal@cihar.com>
Single place to define per browser skips

Signed-off-by: Michal Čihař <michal@cihar.com>
Enabled BrowserStack debug

Signed-off-by: Michal Čihař <michal@cihar.com>