Device node without storage group and timeseries after auto create tiemseries failure

Case: 

1. set storage group to root.a.sg1
2. insert into root.a.d(time, s) values(1, 1)

If the system is using default config, default sglevel = 1, then root.a won't be set as storage group because of storage group root.a.sg1.

However, the node root.a.d will be created. Only after set storage group under child of root.a.d, none sg or timeseries operation on root.a.d could be operated, which means user can't set storage group to root.a.d or create timeseries under root.a.d. 

The node root.a.d can't be deleted because there's no device node delete operation.