Get rid of hack needed to build all armhf projects only on certain builders

[Guilherme Salgado]

AIUI, it should be possible to dispatch armhf projects to any armv7l builders, but currently only one of our armv7l builders is configured to build armhf binaries so we needed a small hack to send all the arhmf builds to that specific builder (see the comment on http://bazaar.launchpad.net/~salgado/offspring/linaro-new/revision/123).

Once all our armv7l builders are setup to build armhf binaries, we should be able to reconfigure anasl (a builder registered in offspring.l.o with armhf as its architecture, and the one to which we send all armhf builds) as an armv7l builder and get rid of that hack. At that time we'll also need to change the mapping in dispatchBuilds() to map 'armhf' projects to armv7l builders so that our armhf projects can be dispatched to any armv7l builders.