Unregister dbus signal callbacks at the end of each subtest.

Callbacks from previous tests were being called and generating errors.
However, since the previous test was complete, these errors were not
stopping execution and failing the test.

TEST=this is a test.  It passes cleanly now.
BUG=chromium-os:14495

Change-Id: I84e748e7683bd7b073e3b23a2e7709f79ce8e243
Reviewed-on: http://gerrit.chromium.org/gerrit/7530
Reviewed-by: Jason Glasgow <jglasgow@chromium.org>
Tested-by: David Rochberg <rochberg@chromium.org>
1 file changed