fix: avoid blocking on appearance dbus call

[BLumia]

避免 appearance 获取壁纸卡死

PMS: BUG-290147
Log:

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关键摘要:

• 在修改后的代码中，m_dbusAppearanceIface->setSync(false); 和 m_dbusAppearanceIface->setUseCache(true); 的调用可能会影响DBus接口的同步性和缓存策略，需要确认这些设置是否符合预期的行为。
• connect 语句中的 lambda 表达式捕获了 this 指针，这是一个常见的做法，但需要确保在 lambda 表达式中不会导致循环引用，从而影响对象的生命周期。

是否建议立即修改:

• 是，需要确保修改后的代码不会引入新的问题，并且与预期的行为一致。同时，应该进行充分的测试来验证这些更改的正确性。