Add test to cover run_list concatenation.
DataMunger - Support legacy require_chef_omnibus values in driver.

This effectively converts:

    ---
    driver:
      require_chef_omnibus: 11.6.2
    platforms:
    - name: ubuntu-12.04
      driver:
        require_chef_omnibus: 11.8.0
    suites:
    - name: server
      driver:
        require_chef_omnibus: true

into:

    ---
    provisioner:
      require_chef_omnibus: 11.6.2
    platforms:
    - name: ubuntu-12.04
      provisioner:
        require_chef_omnibus: 11.8.0
    suites:
    - name: server
      provisioner:
        require_chef_omnibus: true

This will be supported in the near-term for backwards compatibility,
then a future release will deprecate this legacy usage with a warning
message when encountered, then the legacy support will be finally
removed in another release.

Thanks to @preed for the helpful test case data! <3