Client name should not be coupled to node name.

I was recently trying to use a specific client name and key and was failing miserably. It turns out that client key and client name are not set properly during chef-client runs and instead are coupled to the node name. This decouples the two if the user defines `client_name` in their `client.rb` file.
I agree overriding is not a good idea but I didn't want to track down all call sites and fix them. For my use case this was sufficient to fix my problem. The proper solution is to find all the places the client_name is passed in and make sure it is correct and respects whatever value is set in the configuration.