[213] Workaround missing assertIsInstance

Some systems don't seem to have it.

src/lib/python/isc/bind10/tests/component_test.py

@@ -466,7 +466,8 @@ class ComponentTests(BossUtils, unittest.TestCase):
         self.assertEqual({}, self.__registered_processes)
         component.start()
         self.assertTrue(component.running())
-        self.assertIsInstance(component._procinfo, TestProcInfo)
+        # Some versions of unittest miss assertIsInstance
+        self.assertTrue(isinstance(component._procinfo, TestProcInfo))
         self.assertEqual(42, component.pid())
         self.assertEqual(component, self.__registered_processes.get(42))