status checker now only tries to lock the manager, it won't wait anymore.
* Added MediaChanged() and UpdateMediaStatusIfNeeded() methods to KDiskDevice.
* KDiskDeviceManager::_CheckMediaStatus() now uses these new methods; it should
no longer detect removed media more than once :-)
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22621 a95241bf-73f2-0310-859d-f6bbb57e9c96