Try fix for failing config test

We keep seeing this randomly
```
1) Chef::WorkstationConfigLoader loading the config file when the config file exists and raises a ruby exception during evaluation raises a ConfigurationError
   Failure/Error: expect { config_loader.load }.to raise_error(Chef::Exceptions::ConfigurationError)
     expected Chef::Exceptions::ConfigurationError, got #<Errno::ENOENT: No such file or directory @ rb_sysopen - /tmp/Chef-WorkstationConfigLoader-rspec-test20150707-35300-f9yfb6> with backtrace:
       # ./lib/chef/workstation_config_loader.rb:164:in `readlines'
       # ./lib/chef/workstation_config_loader.rb:164:in `highlight_config_error'
       # ./lib/chef/workstation_config_loader.rb:156:in `rescue in read_config'
       # ./lib/chef/workstation_config_loader.rb:137:in `read_config'
       # ./lib/chef/workstation_config_loader.rb:72:in `load'
       # ./spec/unit/workstation_config_loader_spec.rb:275:in `block (6 levels) in <top (required)>'
       # ./spec/unit/workstation_config_loader_spec.rb:275:in `block (5 levels) in <top (required)>'
   # ./spec/unit/workstation_config_loader_spec.rb:275:in `block (5 levels) in <top (required)>'
```

I think the issue is that the tempfile gets GC'd, and when it gets GC'd, it deletes the file.
If it is cleaned up before it is used, then the test fails.

Decommission 12-stable

Removes 12-stable from travis.yml branch filter
Updates appveyor.yml for the 12.4-stable branch

Move Chef::OscUser back to Chef::User namespace and new user code to Chef::UserV1.