mutually exclusive classes set

This is an offshot of #1436 . Based on information in that report, I wrote a policy which consistently yields inconsistent results.

<pre>
#
body common control {

bundlesequence =>

{ "test" }

;
}

bundle agent test {
storage:
"/boot"
volume => min_free_space,
classes => set_class("boot_good", "boot_nogood");

reports:
boot_good::
"/boot has enough space";
boot_nogood::
"/boot does not have enough space";
}

body volume min_free_space
{
freespace => "200G";
}

body classes set_class(boot_good,boot_nogood)
{
promise_kept =>

{ "$(boot_good)" }

;
repair_failed =>

{ "$(boot_nogood)" }

;
}
</pre>

I can get no reports at all, I can get a fail, or a pass and fail at the same time:

<pre>
2014-04-08T16:35:42+0200 error: /default/test/storage/'/boot'[0]: Disk space under 209715200 kB for volume containing '/boot' (435063 kB free)
R: /boot has enough space
R: /boot does not have enough space
</pre>