FdoSecrets: handle corner cases in collection dbus names, fix #5279

- Use completeBaseName rather than baseName to ensure nonempty name
- Handle two databases have the same name
- Cleanup Service::onDatabaseTabOpened logic

tests/gui/TestGuiFdoSecrets.h

@@ -84,6 +84,9 @@ private slots:
     void testExposeSubgroup();
     void testModifyingExposedGroup();
 
+    void testHiddenFilename();
+    void testDuplicateName();
+
 protected slots:
     void createDatabaseCallback();