Use alpine based linux with pxelinux.0 binary

[shivarammysore]

Context

The current version uses CentOS. You can use Alpine Linux for a much reduced container size. You can use Alpine packagestftp-hpa, dhcp-server-vanilla and syslinux - https://pkgs.alpinelinux.org/packages . Go can provide HTTP service.

Possible Fix

Update Dockerfile to use Alpine Linux