Moving shared code to mediawiki-selenium Ruby gem

Bug: 53579
Change-Id: I3164a9640ec878723b622f42c7684ffdeedf9d8c

tests/browser/features/step_definitions/common_steps.rb

@@ -6,7 +6,7 @@ Given(/^I am logged out$/) do
 end
 
 Given(/^I am logged in$/) do
-	visit(LoginPage).login_with(@mediawiki_username, ENV['MEDIAWIKI_PASSWORD'])
+	visit(LoginPage).login_with(ENV['MEDIAWIKI_USER'], ENV['MEDIAWIKI_PASSWORD'])
 	# Assert that login worked
 	loggedin = !@browser.execute_script( "return mw.user.isAnon();" )
 	loggedin.should be_true