Refactor cucumber tags and steps

Use @mocked_home_directory provided by aruba and remove our custom
@fake_home tag.

features/ssh/config.feature

@@ -14,7 +14,7 @@ Feature: SSH settings
     When I successfully execute the recipe
     Then the output must contain my current login name
 
-  @fake_home
+  @mocked_home_directory
   Scenario: uses configured SSH user name for a given host
     Given an SSH config with:
       """

lib/producer/core/testing/cucumber.rb

@@ -26,11 +26,6 @@ Before('~@exec') do
   Aruba.process = Aruba::InProcess
 end
 
-# Fake home directory for @fake_home tagged scenarios.
-Before('@fake_home') do
-  ENV['HOME'] = File.expand_path(current_dir)
-end
-
 # Enable cucumber-sshd "fast" mode (persists sshd across scenarios), and
 # register hooks for @sshd tagged scenarios.
 Before do