Resolve code coverage error by a new unit test case

Author: ecsonic

tests/component_base_test.py

@@ -0,0 +1,7 @@
+from sonic_platform_base.component_base import ComponentBase
+
+class TestComponentBase:
+
+    def test_get_firmware_update_notification(self):
+        cpnt = ComponentBase()
+        assert(cpnt.get_firmware_update_notification(None) == "None")