Add new "redis-basics-persistent" test to verify persistence

[tianon]

This won't pass as-is until redis/docker-library-redis#59 is merged (intentionally), but this will allow us to ensure the expected behavior continues to work appropriately in the future.

[tianon]

I've updated this to include the change from redis/docker-library-redis#59 directly so it's easier to test properly. 👍

[tianon]

(This will help us avoid a repeat of redis/docker-library-redis#58)

[tianon]

Build test of #1724; 4136b5e (redis):

$ bashbrew build "redis"
Cloning redis (git://github.com/docker-library/redis) ...
Processing redis:2.8.23 ...
Processing redis:2.8 ...
Processing redis:2 ...
Processing redis:2.8.23-32bit ...
Processing redis:2.8-32bit ...
Processing redis:2-32bit ...
Processing redis:3.0.7 ...
Processing redis:3.0 ...
Processing redis:3.0.7-32bit ...
Processing redis:3.0-32bit ...
Processing redis:3.0.7-alpine ...
Processing redis:3.0-alpine ...
Processing redis:3.2.0 ...
Processing redis:3.2 ...
Processing redis:3 ...
Processing redis:latest ...
Processing redis:3.2.0-32bit ...
Processing redis:3.2-32bit ...
Processing redis:3-32bit ...
Processing redis:32bit ...
Processing redis:3.2.0-alpine ...
Processing redis:3.2-alpine ...
Processing redis:3-alpine ...
Processing redis:alpine ...
$ bashbrew list --uniq "$url" | xargs test/run.sh
testing redis:2.8.23
    'utc' [1/6]...passed
    'cve-2014--shellshock' [2/6]...passed
    'no-hard-coded-passwords' [3/6]...passed
    'override-cmd' [4/6]...passed
    'redis-basics' [5/6]...passed
    'redis-basics-persistent' [6/6]...passed
testing redis:2.8.23-32bit
    'utc' [1/6]...passed
    'cve-2014--shellshock' [2/6]...passed
    'no-hard-coded-passwords' [3/6]...passed
    'override-cmd' [4/6]...passed
    'redis-basics' [5/6]...passed
    'redis-basics-persistent' [6/6]...passed
testing redis:3.0.7
    'utc' [1/6]...passed
    'cve-2014--shellshock' [2/6]...passed
    'no-hard-coded-passwords' [3/6]...passed
    'override-cmd' [4/6]...passed
    'redis-basics' [5/6]...passed
    'redis-basics-persistent' [6/6]...passed
testing redis:3.0.7-32bit
    'utc' [1/6]...passed
    'cve-2014--shellshock' [2/6]...passed
    'no-hard-coded-passwords' [3/6]...passed
    'override-cmd' [4/6]...passed
    'redis-basics' [5/6]...passed
    'redis-basics-persistent' [6/6]...passed
testing redis:3.0.7-alpine
    'utc' [1/6]...passed
    'cve-2014--shellshock' [2/6]...passed
    'no-hard-coded-passwords' [3/6]...passed
    'override-cmd' [4/6]...passed
    'redis-basics' [5/6]...passed
    'redis-basics-persistent' [6/6]...passed
testing redis:3.2.0
    'utc' [1/6]...passed
    'cve-2014--shellshock' [2/6]...passed
    'no-hard-coded-passwords' [3/6]...passed
    'override-cmd' [4/6]...passed
    'redis-basics' [5/6]...passed
    'redis-basics-persistent' [6/6]...passed
testing redis:3.2.0-32bit
    'utc' [1/6]...passed
    'cve-2014--shellshock' [2/6]...passed
    'no-hard-coded-passwords' [3/6]...passed
    'override-cmd' [4/6]...passed
    'redis-basics' [5/6]...passed
    'redis-basics-persistent' [6/6]...passed
testing redis:3.2.0-alpine
    'utc' [1/6]...passed
    'cve-2014--shellshock' [2/6]...passed
    'no-hard-coded-passwords' [3/6]...passed
    'override-cmd' [4/6]...passed
    'redis-basics' [5/6]...passed
    'redis-basics-persistent' [6/6]...passed

[yosifkit]

LGTM