Local chroot support v2

Add support for acting on a local chroot. This could be used for building a preconfigured virtual OS image starting from a raw distro bootstrap.

Requires running ansible as `root`.

Includes two fixes for fails when `/proc` is not mounted.

Using
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Example of use with a Debian boostrap:

    $ sudo deboostrap squeeze /tmp/squeeze-chroot
    $ sudo chroot /tmp/squeeze-chroot apt-get update
    $ sudo chroot /tmp/squeeze-chroot apt-get -V --no-install-recommends install python python-apt
    $ sudo -E ansible-playbook -vvv -c chroot -i '/tmp/squeeze-chroot,' all -m setup
    $ sudo -E ansible-playbook -vvv -c chroot -i '/tmp/squeeze-chroot,' test-playbook.yml

an example `test-playbook.yml` could be:

    ---
    - hosts: all
      tasks:
        - name: echo something to temp
          shell: "echo Yaaayy!" >/tmp/foobar.txt

        - name: installs a package
          apt: pkg=less state=latest

Notes
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Same as #2082 but now `chroot` is an independent connection type as suggested.