fix: [server] exit server when PrepareForShutdown emitted.

[itsXuSt]

to make server exit before udisksd when shutdown/reboot.

Log: as title.

[deepin-bot]

TAG Bot

New tag: 6.0.47
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #1945

[deepin-bot]

TAG Bot

New tag: 6.0.48
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #1949

[deepin-bot]

TAG Bot

New tag: 6.0.49
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #1967

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在Core::start函数中增加了对QDBusConnection::systemBus().connect的调用，但没有检查连接是否成功，可能会导致未处理的连接失败情况。
• Core::exitOnShutdown函数中直接使用qApp->exit(0)进行退出，但没有释放资源或执行清理工作。
• Core::exitOnShutdown函数的参数名称为shutdown，但实际传入的是一个布尔值，可能会引起误解。建议使用更明确的参数名，如isShutdown。

是否建议立即修改:

• 是

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: itsXuSt, Johnson-zs

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[itsXuSt]

/merge