Mistral does not always detect unreachable task with join

The following workflow remains in RUNNING instead of changing to ERROR.

"task_b_1" fails and Mistral should know that "task_with_join" is now unreachable and should be changed from WAITING to ERROR.

---
version: "2.0"
test_join_wf:
  tasks:
    task_a_1:
      action: std.noop
      on-success:
        - task_with_join

    task_b_1:
      action: std.http
      input:
        url: "http://1.1.1.1"
      on-success:
        - task_b_2

    task_b_2:
      action: std.noop
      on-success:
        - task_b_3

    task_b_3:
      action: std.noop
      on-success:
        - task_with_join

    task_with_join:
      action: std.noop
      join: all

CLI output:

[15:02 cbnd@cbnd-785-application ~] > mistral execution-create test_join_wf
+-------------------+--------------------------------------+
| Field | Value |
+-------------------+--------------------------------------+
| ID | 17849d1c-c684-417a-8cd8-bcd9e97ab009 |
| Workflow ID | 40f1e26a-4f55-44d1-932e-ede437fed7ef |
| Workflow name | test_join_wf |
| Description | |
| Task Execution ID | <none> |
| State | RUNNING |
| State info | None |
| Created at | 2016-10-24 12:02:08.615491 |
| Updated at | 2016-10-24 12:02:08.619341 |
+-------------------+--------------------------------------+
[15:02 cbnd@cbnd-785-application ~] > mistral task-list 17849d1c-c684-417a-8cd8-bcd9e97ab009
+--------------------------------------+----------------+---------------+--------------------------------------+---------+------------------+
| ID | Name | Workflow name | Execution ID | State | State info |
+--------------------------------------+----------------+---------------+--------------------------------------+---------+------------------+
| 44ff5e2f-eb1e-4d36-8eb2-af8d3db134dd | task_with_join | test_join_wf | 17849d1c-c684-417a-8cd8-bcd9e97ab009 | WAITING | Task is waiting. |
| 7b79267e-c556-4fb0-b887-a73a07b9e977 | task_b_1 | test_join_wf | 17849d1c-c684-417a-8cd8-bcd9e97ab009 | RUNNING | None |
| ee8d64ee-470d-4710-9a0a-a3823bc86d8f | task_a_1 | test_join_wf | 17849d1c-c684-417a-8cd8-bcd9e97ab009 | SUCCESS | None |
+--------------------------------------+----------------+---------------+--------------------------------------+---------+------------------+
[15:02 cbnd@cbnd-785-application ~] > mistral task-list 17849d1c-c684-417a-8cd8-bcd9e97ab009
+--------------------------------------+----------------+---------------+--------------------------------------+---------+------------------------------+
| ID | Name | Workflow name | Execution ID | State | State info |
+--------------------------------------+----------------+---------------+--------------------------------------+---------+------------------------------+
| 44ff5e2f-eb1e-4d36-8eb2-af8d3db134dd | task_with_join | test_join_wf | 17849d1c-c684-417a-8cd8-bcd9e97ab009 | WAITING | Task is waiting. |
| 7b79267e-c556-4fb0-b887-a73a07b9e977 | task_b_1 | test_join_wf | 17849d1c-c684-417a-8cd8-bcd9e97ab009 | ERROR | Failed to run action [act... |
| ee8d64ee-470d-4710-9a0a-a3823bc86d8f | task_a_1 | test_join_wf | 17849d1c-c684-417a-8cd8-bcd9e97ab009 | SUCCESS | None |
+--------------------------------------+----------------+---------------+--------------------------------------+---------+------------------------------+
[15:11 cbnd@cbnd-785-application ~] > mistral execution-get 17849d1c-c684-417a-8cd8-bcd9e97ab009
+-------------------+--------------------------------------+
| Field | Value |
+-------------------+--------------------------------------+
| ID | 17849d1c-c684-417a-8cd8-bcd9e97ab009 |
| Workflow ID | 40f1e26a-4f55-44d1-932e-ede437fed7ef |
| Workflow name | test_join_wf |
| Description | |
| Task Execution ID | <none> |
| State | RUNNING |
| State info | None |
| Created at | 2016-10-24 12:02:08 |
| Updated at | 2016-10-24 12:02:08 |
+-------------------+--------------------------------------+