(#20768) Refactor base profile logic

This commit refactors the logic for figuring out the base profile
directory, e.g. C:\Users or C:\Documents and Settings, and updates the
acceptance test to use it. The `--helper` option must be used in the
systest harness so that the LOAD_PATH is setup correctly to find the
windows_utils.rb helper, but this should already be the case for
temp_file_utils.rb, etc.
(#20768) Windows can now create the home directory (again)

The previously pending_test method was used, because puppet couldn't
create the home directory when creating the user in ruby 1.9 on windows.
Now that that is resolved, we can remove the windows-specific
pending_test. Note, that the test will still be pending later, since
neither the windows nor useradd providers correctly move the user's home
directory.