Tests for PXE bare-metal provisioning helper server.

a part of blueprint general-bare-metal-provisioning-framework.

The deploy helper was landed without tests. This patch reinstates the
tests.

Change-Id: I690ec077e175dc37c2cc5f18170513b0e5bca103
Co-authored-by: Mikyung Kang <mkkang@isi.edu>
Co-authored-by: David Kang <dkang@isi.edu>
Co-authored-by: Ken Igarashi <igarashik@nttdocomo.co.jp>
Co-authored-by: Arata Notsu <notsu@virtualtech.jp>
Co-authored-by: Devananda van der Veen <devananda.vdv@gmail.com>
Merge "Tests for PXE bare-metal provisioning helper server."