binman: Fix up removal of temporary directories

At present 'make check' leaves some temporary directories around. Part of
this is because we call tools.PrepareOutputDir() twice in some cases,
without calling tools.FinaliseOutputDir() in between.

Fix this.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/binman/fdt_test.py

@@ -21,6 +21,10 @@ class TestFdt(unittest.TestCase):
         self._indir = tempfile.mkdtemp(prefix='binmant.')
         tools.PrepareOutputDir(self._indir, True)
 
+    @classmethod
+    def tearDownClass(self):
+        tools._FinaliseForTest()
+
     def TestFile(self, fname):
         return os.path.join(self._binman_dir, 'test', fname)