[CHEF-4842] Fix comparison of user resources with non-ASCII comments

In case a comment of a user resource includes non-ASCII characters, the
comparison whether the resource was changed will always fail. Therefore,
such user resources will get modified during every chef-client run.

Example:

    user "marci" do
      comment "Márton Salomváry"
      # ...
    end

So far, this resulted in a comparision of "M\xC3\xA1rton
Salomv\xC3\xA1ry" with "Márton Salomváry" which fails, unless the
encoding gets changed prior to the comparision.

https://tickets.opscode.com/browse/CHEF-4842