QA: Fixed Selenium tests that fail during login at Cloudbees

MEDIAWIKI_PASSWORD environment variable will be correctly set only if
the scenario is tagged with Cucumber tag @login[1]

1:
https://github.com/wikimedia/mediawiki-selenium/blob/master/lib/mediawik
i_selenium/support/hooks.rb#L17

Bug: 62350
Change-Id: I207f381c02c88f7a1c2e24def99afe9852a90efc
Merge "QA: Fixed Selenium tests that fail during login at Cloudbees"