Moved login and reset preferences to mediawiki_selenium Ruby gem

Bug: 56088
Change-Id: I3d4150295ec2f66e5ad20a90769b7bd4bb14763f

tests/browser/features/step_definitions/common_steps.rb

@@ -5,10 +5,6 @@ end
 Given(/^I am logged out$/) do
 end
 
-Given(/^I am logged in$/) do
-	visit(LoginPage).login_with(ENV["MEDIAWIKI_USER"], ENV["MEDIAWIKI_PASSWORD"])
-end
-
 Given(/^I set "(.*?)" as the interface language$/) do |language|
 	code = on(PanelPage).language_to_code(language)
 	visit(PanelPage, :using_params => {:extra => "setlang=#{code}"})