bootstrap fails cause pkg2ng has been removed from pkg

[jltignon]

Hi bsdploy developers,

Beginning with 1.10 version, pkg2ng has been removed from pkg, so bootstrap fails with the following error :

[root@rock] run: chroot /mnt pkg2ng
[root@rock] out: chroot: pkg2ng: No such file or directory
[root@rock] out:

Since pkg2ng was used on old FreeBSD systems using the pkg_* commands, maybe it can be safely removed from bsdploy/bootstrap_utils.py.

What do you think ?