Add generic packer templates

Add generic packer templates

- Packer jobs are designed to validate packer files and build
  custom images on the cloud. The packer templates can be used for
  and LF projects which clone global-jjb submodule.
- The jobs check if packer binaries are unavailable and install packer
  on the build node. The default version of packer installed is 1.0.2
  while more recent version can be defined in the job.
- Update test templates according to new packer jobs introduced.

Change-Id: I3657621e30d402655b84973ea4b4c48fa21cea2d
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>
Signed-off-by: Andrew Grimberg <agrimberg@linuxfoundation.org>