Update Alpine images for root su passwordless bug

[andyshinn]

References gliderlabs/docker-alpine#101, gliderlabs/docker-alpine#107 and gliderlabs/docker-alpine#109.

[frol]

According to #1240 you may want to add "[Security]" to your PR name.

[yosifkit]

LGTM, Build test of #1292; 0a4c6dc (alpine):

$ bashbrew build "alpine"
Cloning alpine (git://github.com/gliderlabs/docker-alpine) ...
Processing alpine:2.6 ...
Processing alpine:2.7 ...
Processing alpine:3.1 ...
Processing alpine:3.2 ...
Processing alpine:latest ...
Processing alpine:edge ...
$ bashbrew list --uniq "$url" | xargs test/run.sh
testing alpine:2.6
    'utc' [1/4]...passed
    'cve-2014--shellshock' [2/4]...passed
    'no-hard-coded-passwords' [3/4]...passed
    'override-cmd' [4/4]...passed
testing alpine:2.7
    'utc' [1/4]...passed
    'cve-2014--shellshock' [2/4]...passed
    'no-hard-coded-passwords' [3/4]...passed
    'override-cmd' [4/4]...passed
testing alpine:3.1
    'utc' [1/4]...passed
    'cve-2014--shellshock' [2/4]...passed
    'no-hard-coded-passwords' [3/4]...passed
    'override-cmd' [4/4]...passed
testing alpine:3.2
    'utc' [1/4]...passed
    'cve-2014--shellshock' [2/4]...passed
    'no-hard-coded-passwords' [3/4]...passed
    'override-cmd' [4/4]...passed
testing alpine:edge
    'utc' [1/4]...passed
    'cve-2014--shellshock' [2/4]...passed
    'no-hard-coded-passwords' [3/4]...passed
    'override-cmd' [4/4]...passed

[yosifkit]

Changeset: gliderlabs/docker-alpine@da7426c...4cc44a3