create-image.sh: disk image generation now supports grub1 based distribution

Add grub1 support when generating virtual disk image. However we use extlinux
as installing grub1 in a chroot is not very reliable.

During the virtual disk image creation the bootloader installation process
detect whether grub2 is available or not, if not extlinux is used.
create-image.sh: basic network config for redhat based linux

When generating virtual disk image for redhat based linux, the automatic
network configuration settings is now properly handled. ndp is also
functionnal.
Merge branch 'master' of github.com:enovance/edeploy

Re-sync with upstream, solve simple minor conflict:
	build/create-image.sh
Merge branch 'master' of github.com:moxxxom/edeploy into moxxxom-master

By Pierre Rognant
* 'master' of github.com:moxxxom/edeploy:
  create-image.sh: basic network config for redhat based linux
  create-image.sh: disk image generation now supports grub1 based distribution