Deleted tasks are still enabled and can't be disabled or deleted

Nobody has claimed this yet.

Kapacitor 1.1.0 (git: master 939fdf670b028c142944977dcfcb045cac2343ed)
Ubuntu 14.04.5 LTS

When I define a kapacitor task like:

```
kapacitor define healthcheck_alert ...
```

and then delete it like:

```
kapacitor delete tasks healthcheck_alert
```

the task seems to become a 'zombie'. It is not shown when running `kapacitor list tasks`, but running `kapacitor show healthcheck_alert` shows:

```
ID: healthcheck_alert
Error:
Template:
Type: batch
Status: enabled
Executing: true
Created: 29 Nov 16 18:01 UTC
Modified: 29 Nov 16 20:36 UTC
LastEnabled: 29 Nov 16 20:36 UTC
Databases Retention Policies: ["service_status"."autogen"]
...
```

I now can't seem to delete, define, enable or disable this task. These kapacitor commands run without error but the task remains in exactly the same state. It can't be updated, deleted or disabled and is still sending alerts. I've tried to disable and delete this task, but `kapacitor show` still shows it.

Start by reproducing the sequence with `kapacitor define`, `kapacitor delete tasks`, and `kapacitor show`, then compare the behavior of `list`, `enable`, and `disable`. Trace the task lifecycle behind these command entry points and verify that deleting a task removes it from `show` and stops its alerts. There are no files or tests named in the issue.

Written by the indexing model from the issue text.