Commit c5e509c3
added the ability to download from network cache when building re6st,
but slapos.libnetworkcache is imported after bin/buildout has
already been generated. The fixup consists of adding libnetworkcache
in bin/buildout from bin/python, which has been renamed to
bin/python.temp until the end of bootstrap to start again if we fail
before the end of the task.

/reviewed-on !90