Revert "Set `Busser[:sudo]` to `false` by default."

It appears that some platforms (CentOS being one of them) may want to
call certain progrmas as root. Either because of the path to
/sbin/service or other reasons.

Setting Busser configuration option of `sudo` to `true` should enable
a better out-of-the-box experience in the default case and still
allows for this setting to be overriden in a busser config block in the
root of the .kitchen.yml document:

    ---
    driver: vagrant
    provisioner: chef_solo

    busser:
      sudo: false

    platforms:
      - name: centos-6.4

    suites:
      - name: server

Or in a platform:

    ---
    driver: vagrant
    provisioner: chef_solo

    platforms:
      - name: centos-6.4
        busser:
          sudo: false

    suites:
      - name: server

Or in a suite:

    ---
    driver: vagrant
    provisioner: chef_solo

    platforms:
      - name: centos-6.4

    suites:
      - name: server
        busser:
          sudo: false

This reverts commit f002ae7c2f054d547d5852035019864d9070a051.

Closes #269
References #273
References #270
References #265