[vserver] support for alpine linux guests

Hi,

Alpine Linux is a distribution for secure light weight
servers/firewalls, based on uclibc/busybox, built using Gentoo
framework.

Attatched is initpre and initpost scripts to allow easy installation of
Alpine Linux guests. It is done in seconds. Create directory
distributions/alpine and save the attatched files there.

To set up a guest:

wget http://dev.alpinelinux.org/alpine/v1.7/base.tar.bz2
vserver alpine-guest build \
    --context 1001 \
    --interface eth0:<ipaddr>/<mask> \
    --hostname alpine-guest -m template -- \
      -t base.tar.bz2 \
      -d alpine

base.tar.bz2 is 700-800 KB and the alpine guest is 2.5MB.

To list available packages, log in and:

export APK_PATH=http://dev.alpinelinux.org/alpine/v1.7/apks
apk_fetch -l

To install a package:
apk_add <package>

It would be nice if next release of util-vserver could include support
for Alpine.

Thanks!

Natanael Copa