Use dhcp_checker as binary call instead of library

[Matthew Mosesohn]

Fuelmenu should use dhcp_checker as a binary call

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/260458

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/260458
Committed: https://git.openstack.org/cgit/openstack/fuel-menu/commit/?id=bd511fdef94fa8e3d6b26098a42c3ec7d206a089
Submitter: Jenkins
Branch: master

commit bd511fdef94fa8e3d6b26098a42c3ec7d206a089
Author: Matthew Mosesohn <email address hidden>
Date: Tue Dec 22 15:04:25 2015 +0300

    Switch dhcpcheck to shell command

    Fuelmenu should call dhcpcheck as an external command,
    rather than as a direct python library.

    Fixed some import order and added test coverage.

    Change-Id: I7c71779d51a5478d5728b7b1dda0673521798a45
    Closes-Bug: #1528543

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/8.0
Review: https://review.openstack.org/261974

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/261974
Committed: https://git.openstack.org/cgit/openstack/fuel-menu/commit/?id=f69e2ffb4a64cb66bd23f9762737504482b200a9
Submitter: Jenkins
Branch: stable/8.0

commit f69e2ffb4a64cb66bd23f9762737504482b200a9
Author: Matthew Mosesohn <email address hidden>
Date: Tue Dec 22 15:04:25 2015 +0300

    Switch dhcpcheck to shell command

    Fuelmenu should call dhcpcheck as an external command,
    rather than as a direct python library.

    Fixed some import order and added test coverage.

    Change-Id: I7c71779d51a5478d5728b7b1dda0673521798a45
    Closes-Bug: #1528543
    (cherry picked from commit bd511fdef94fa8e3d6b26098a42c3ec7d206a089)

[Mikhail Samoylov (msamoylov)]

The work is not seen problems caused by code changes in this bug for fuel version:
[root@nailgun ~]# cat /etc/fuel/version.yaml
VERSION:
  feature_groups:
    - mirantis
  production: "docker"
  release: "8.0"
  api: "1.0"
  build_number: "506"
  build_id: "506"
  fuel-nailgun_sha: "8e954abd70ef0083109f34289de2553dcda544d4"
  python-fuelclient_sha: "4f234669cfe88a9406f4e438b1e1f74f1ef484a5"
  fuel-agent_sha: "658be72c4b42d3e1436b86ac4567ab914bfb451b"
  fuel-nailgun-agent_sha: "b2bb466fd5bd92da614cdbd819d6999c510ebfb1"
  astute_sha: "b81577a5b7857c4be8748492bae1dec2fa89b446"
  fuel-library_sha: "ec7e212972ead554f21b52b9e165156665f659df"
  fuel-ostf_sha: "ab5fd151fc6c1aa0b35bc2023631b1f4836ecd61"
  fuel-mirror_sha: "351d568fa3b3e4dd062054b91d766aa54d379867"
  fuelmenu_sha: "234cb4cbb30fbd2df00f388c28f31606d9cae15f"
  shotgun_sha: "63645dea384a37dde5c01d4f8905566978e5d906"
  network-checker_sha: "a43cf96cd9532f10794dce736350bf5bed350e9d"
  fuel-upgrade_sha: "616a7490ec7199f69759e97e42f9b97dfc87e85b"
  fuelmain_sha: "94507c5e4dad6d8cfbd8f5d41aa8389d5335990a".

Just performed code review, code is clear and should work.