Use aosp as the default remote (instead of linaro) for galaxy-nexus, galaxy-s2, nexus-s-4g, and nexus-s

The linaro remote has apparently become unreliable for running `./config.sh` in the B2G repo.  A number of the submodules at linaro would 404. After asking around in irc.mozilla.org#b2g, Fabrice (the channel op) suggested pointing to aosp instead. This allowed `./config.sh` to install all of the submodules correctly.

This PR is for the v1-train branch. If this should be in another branch let me know. There was no README for the repo, so I wasn't sure.

Thanks!