Fixes #14505 - Correct authorization of broken smart proxy actions

Because the controller is named "smart_proxies" but the puppetca and
autosign actions are implemented in seperate controllers,
authorized_via_my_scope fails to find the correct permission.
This also fixes the link to show proxy when viewing as non-admin user.

(cherry picked from commit a88d4a3e9790bf863634688b286ec6f9eed12907)