added disk systems rescan to DiskDeviceManager, and called it in the post init phase

the next step would be to rescan the partition tree with a job to recognize unrecognized partitions (asynchronously ?)


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@18737 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/disk_device_manager/KDiskDeviceManager.h

@@ -120,6 +120,7 @@ public:
 	// by the registrar.
 
 	status_t InitialDeviceScan();
+	status_t RescanDiskSystems();
 
 private:
 	status_t _AddPartitioningSystem(const char *name);