fix/BROOKLYN-36

fix saveIptablesRules
does `apt-get`ting this package really cause the rules to be saved immediately?  i think you want to second command to be run irrespective of the result of the former.  perhaps also try running `iptables-save` as presumably that worked somewhere, and it might work somewhere that `service iptables save` and `/sbin/service iptables save` doesn't work ... if i've understood correctly?  /cc @grkvlt

i'd suggest (with `import static BashCommands.*` here, for brevity):

    chain(
      ok(install("iptables-persistent")),
      alternatives(
        iptablesService("save"),
        "iptables-save"
    ))