[leo_storage] delete doesn't delete grandchildren

[mocchira]

Reported on https://groups.google.com/forum/#!topic/leoproject_leofs/TFCEFftftu0

After deleting an object having grandchildren, we will get the following with leofs-adm whereis

leofs@cat2neat:leofs.1.3.5$ ./leofs-adm whereis "test/core"
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
 del?  |           node           |             ring address             |    size    |   checksum   |  has children  |  total chunks  |     clock      |             when
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
  *    | storage_0@127.0.0.1      | e686059486bcfc05dd10a3f6b4d4e281     |         0B |   d41d8cd98f | false          |              0 | 5686f566b5799  | 2018-03-28 10:58:04 +0900
  *    | storage_2@127.0.0.1      | e686059486bcfc05dd10a3f6b4d4e281     |         0B |   d41d8cd98f | false          |              0 | 5686f566b5799  | 2018-03-28 10:58:04 +0900

leofs@cat2neat:leofs.1.3.5$ ./leofs-adm whereis "test/core\n1"
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
 del?  |           node           |             ring address             |    size    |   checksum   |  has children  |  total chunks  |     clock      |             when
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
  *    | storage_1@127.0.0.1      | 85004bf741f52151d65e9db8f7f01eb5     |         0B |   d41d8cd98f | false          |              0 | 5686f567210ef  | 2018-03-28 10:58:04 +0900
  *    | storage_3@127.0.0.1      | 85004bf741f52151d65e9db8f7f01eb5     |         0B |   d41d8cd98f | false          |              0 | 5686f567210ef  | 2018-03-28 10:58:04 +0900

leofs@cat2neat:leofs.1.3.5$ ./leofs-adm whereis "test/core\n1\n1"
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
 del?  |           node           |             ring address             |    size    |   checksum   |  has children  |  total chunks  |     clock      |             when
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
       | storage_3@127.0.0.1      | ff712f5cd19c4c1a9269fb430c3d0727     |      5120K |   e3416b078c | false          |              0 | 5686f4c042208  | 2018-03-28 10:55:09 +0900
       | storage_2@127.0.0.1      | ff712f5cd19c4c1a9269fb430c3d0727     |      5120K |   e3416b078c | false          |              0 | 5686f4c042208  | 2018-03-28 10:55:09 +0900

leofs@cat2neat:leofs.1.3.5$ ./leofs-adm whereis "test/core\n1\n2"
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
 del?  |           node           |             ring address             |    size    |   checksum   |  has children  |  total chunks  |     clock      |             when
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
       | storage_2@127.0.0.1      | 7a8a8141834073137e7d08fc2965c135     |      5120K |   60843fb4b9 | false          |              0 | 5686f4c059309  | 2018-03-28 10:55:09 +0900
       | storage_3@127.0.0.1      | 7a8a8141834073137e7d08fc2965c135     |      5120K |   60843fb4b9 | false          |              0 | 5686f4c059309  | 2018-03-28 10:55:09 +0900

leofs@cat2neat:leofs.1.3.5$ ./leofs-adm whereis "test/core\n1\n3"
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
 del?  |           node           |             ring address             |    size    |   checksum   |  has children  |  total chunks  |     clock      |             when
-------+--------------------------+--------------------------------------+------------+--------------+----------------+----------------+----------------+----------------------------
       | storage_0@127.0.0.1      | f6a2857e02149cce7030a378798488b8     |      5120K |   5badbf063f | false          |              0 | 5686f4c089191  | 2018-03-28 10:55:09 +0900
       | storage_2@127.0.0.1      | f6a2857e02149cce7030a378798488b8     |      5120K |   5badbf063f | false          |              0 | 5686f4c089191  | 2018-03-28 10:55:09 +0900