Skip 3694 warnings on trivial resource cloning

Turns the 3694 warning into a debug message if the prior resource is
identical to the current resource.  Suggestion for opscode/chef-rfc#76
`:@elapsed_time` is only updated at converge time, we can do that to try to allow cloning resources that were forced to converge at compile time, but i'm not sure that'll work well.  `:@enclosing_provider` i don't think matters at all since we'd be in a use_inline_resources provider there.