non-static gdmaps object for unit test boilerplate

The address sanitizer in clang-3.5 is getting more strict about
leak reports and wants to report on static globals that aren't
free()d; this is mostly a workaround for that (the real gdmaps
object for the daemon isn't static and exists for the life of the
daemon and cleanup code for it doesn't exist anymore).
add comment about sanitizers + ccache