buildman: Reinstate removal of temp output dir in tests

This was dropped my mistake. Reinstate it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Fixes: d829f1217c6 ("bulidman: Add support for a simple build")
diff --git a/tools/buildman/func_test.py b/tools/buildman/func_test.py
index b4f3b46..3753551 100644
--- a/tools/buildman/func_test.py
+++ b/tools/buildman/func_test.py
@@ -211,7 +211,7 @@
 
     def tearDown(self):
         shutil.rmtree(self._base_dir)
-        #shutil.rmtree(self._output_dir)
+        shutil.rmtree(self._output_dir)
 
     def setupToolchains(self):
         self._toolchains = toolchain.Toolchains()