update to chefspec 4.1.0

syntax updated to use the new chefspec-4.1.0 way of doing things, no functional changes.

* update chefspec and chef dependencies (chefspec-4.1.0 needs at least chef 11.14)
* remove deprecated explicit require of chefspec/server
* change ChefSpec::Runner into ChefSpec::ServerRunner
* construct data bags inset chef_run block

For details, see https://github.com/sethvargo/chefspec/blob/master/CHANGELOG.md