Tags are not deleted properly when image is deleted

[vholer]

$ canga list
NAME                                                      SIZE DAYS_AGO
  default:ubuntu1610                                  325.4 Mb      0.1
^ default:ubuntu1610/one                               38.9 Mb      0.1
    OpenNebula Compatible Ubuntu 16.10                         
$ canga del ubuntu1610/one
$ canga list
NAME                                                      SIZE DAYS_AGO
  default:ubuntu1610                                  325.4 Mb      0.1
$ cat .cangallo/default/index.yaml 
---
version: 0
images:
  25dbea28c7d75a159c54ed424c5186fefff751fb7d61c75248c4250d893223bc:
    virtual-size: 2361393152
    format: qcow2
    ...
tags:
  ubuntu1610: 25dbea28c7d75a159c54ed424c5186fefff751fb7d61c75248c4250d893223bc
  ubuntu1610/one: d7d895caabef4d31d141d24eb2d357312f4491d8569bffcc5a1a85e3352a35c8

But the tag is still there and can't be deleted:

$ canga deltag ubuntu1610/one
Image "ubuntu1610/one" not found

And blocks future builds with same tag.

[jfontan]

Now all the tags with the image's SHA256 are deleted.