[Reviewer: Andy] Add init.d functions to quiesce/unquiesce and use them on sprout uninstall

Andy,

Please can you review this one too?  I've added a few functions to init.d to quiesce/unquiesce bono and sprout, and then enhanced sprout's uninstall script to use the function.  I haven't enhanced bono's uninstall, because bono quiesce can take a while (and so can be quite inconvenient), and we don't actually require it for now.  Tested live.

Another pull request will be following shortly to enhance chef to use these functions (rather than duplicating knowledge there).

Matt