Duplication of tag deletion events

Summary

• When deleting a tag, a corresponding tag deletion event is created twice
  • as a consequence, a duplicate mail (with a missing footer ...) is sent if configured under services/email_on_push

Steps to reproduce

• Can be reproduced on Self-hosted or Gitlab.com-hosted repositories
• Latest version (11.11.0), as well as Gitlab Next

Example Project

https://gitlab.com/Hottemax/soccer-simulation

What is the current bug behavior?

• tag deletion event is duplicated, can be verified in Project > Activity, where it appears twice

What is the expected correct behavior?

• only a single tag deletion event is triggered

/label gitlab-ce~2278648