Disable Performance bar shortcut for non-admin users
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### Summary
Disable Performance bar shortcut for non-admin users
### Steps to reproduce
1. Login in as non-admin user
1. Press `p b`
1. The page will reload
### What is the expected *correct* behavior?
The Page should not reload and not save the `perf_bar_enabled` cookie
### Relevant logs and/or screenshots
`perf_bar_enabled` **Cookie** (Removed some other cookies for security reasons)

### Output of checks
This bug happens on GitLab.com
### Possible fixes
Set Roles to this line with **if conditions**
https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/assets/javascripts/behaviors/shortcuts/shortcuts.js#L26
issue