Can't unpin blocks when leaving thread

[flyskywhy]

Describe the bug
#244 said Unpin all blocks and data when leaving thread and that issue is closed, but the "unpin" is not working.

To Reproduce
Steps to reproduce the behavior:

1. textile init
2. start textile daemon
3. textile threads add "foobar" --blob -t open -s shared
4. textile messages add THE_FOOBAR_THREAD_ID "a5a5A5A5" and see the BLOCK_ID QmbMCEYu2HUkp7DcYX6SHW2o4dmEDTdSqfNKwMCxWsVHS8
5. stop textile daemon to use ipfs command later
6. IPFS_PATH=~/.textile/repo/ ipfs pin ls | sort and found the BLOCK_ID QmbMCEYu2HUkp7DcYX6SHW2o4dmEDTdSqfNKwMCxWsVHS8
7. start textile daemon
8. textile threads abandon THE_FOOBAR_THREAD_ID
9. stop textile daemon to use ipfs command later
10. IPFS_PATH=~/.textile/repo/ ipfs pin ls | sort and the BLOCK_ID QmbMCEYu2HUkp7DcYX6SHW2o4dmEDTdSqfNKwMCxWsVHS8 still exist!

Even more pin grows, see logs by IPFS_PATH=~/.textile/repo/ ipfs pin ls | sort with each steps above:
after step 2(just init and daemon):

  QmRe5yEoGDVKog9TwhDTotAS3zvN6E8ZtGVH7La3w3XQ1y direct
  QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn recursive
  QmXvw4YgmyfHt7iYzmjVQBdJW7T1oFrZmiMSj2cFBBdL9H direct

after step 3(threads add):

+ QmbVG16LQp3h1bBhztbRTcEGTo4ke3z2hN1uu53voqyTge direct
+ QmQn4hHm42sou9YFWSCAsmHJ7kCAf2cXU9TXQTxS5CLdvL direct
  QmRe5yEoGDVKog9TwhDTotAS3zvN6E8ZtGVH7La3w3XQ1y direct
  QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn recursive
+ QmX5hDjNCbxPqoeRFQu2Jv5A41MyYYAa3TPYuB4wvorwJj direct
  QmXvw4YgmyfHt7iYzmjVQBdJW7T1oFrZmiMSj2cFBBdL9H direct

after step 4(messages add):

+ QmbMCEYu2HUkp7DcYX6SHW2o4dmEDTdSqfNKwMCxWsVHS8 direct
  QmbVG16LQp3h1bBhztbRTcEGTo4ke3z2hN1uu53voqyTge direct
+ QmdhsrtMquh8wXmBxbhiqAqGVujhi5Ycg946Qznk1qxnyW direct
+ QmQ7gfxv5WXcrvvjUS2La57ujb4L8mdAGXZ3xk7Nto5TPJ direct
  QmQn4hHm42sou9YFWSCAsmHJ7kCAf2cXU9TXQTxS5CLdvL direct
  QmRe5yEoGDVKog9TwhDTotAS3zvN6E8ZtGVH7La3w3XQ1y direct
  QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn recursive
  QmX5hDjNCbxPqoeRFQu2Jv5A41MyYYAa3TPYuB4wvorwJj direct
  QmXvw4YgmyfHt7iYzmjVQBdJW7T1oFrZmiMSj2cFBBdL9H direct

after step 8(threads abandon):

  QmbMCEYu2HUkp7DcYX6SHW2o4dmEDTdSqfNKwMCxWsVHS8 direct
  QmbVG16LQp3h1bBhztbRTcEGTo4ke3z2hN1uu53voqyTge direct
  QmdhsrtMquh8wXmBxbhiqAqGVujhi5Ycg946Qznk1qxnyW direct
  QmQ7gfxv5WXcrvvjUS2La57ujb4L8mdAGXZ3xk7Nto5TPJ direct
  QmQn4hHm42sou9YFWSCAsmHJ7kCAf2cXU9TXQTxS5CLdvL direct
  QmRe5yEoGDVKog9TwhDTotAS3zvN6E8ZtGVH7La3w3XQ1y direct
+ QmSMakugWZHYCpT35rSV9DDdgxEwbvCydRMjqaLMCdke6u direct
  QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn recursive
  QmX5hDjNCbxPqoeRFQu2Jv5A41MyYYAa3TPYuB4wvorwJj direct
  QmXvw4YgmyfHt7iYzmjVQBdJW7T1oFrZmiMSj2cFBBdL9H direct

Expected behavior
Should unpin the BLOCK_ID comes from message. Even should unpin more HASH refer to the "+" symbol I added in logs.

CLI:

• OS: Linux Ubuntu 19.04
• Version textile 0.4.1 and 0.6.1