Merge branch 'docs/AuthorizedKeysCommand-by-default-in-Docker' into 'master'

Documentation for AuthorizedKeysCommand enabled by default in Docker

See merge request gitlab-org/gitlab-ce!27184

doc/administration/operations/fast_ssh_key_lookup.md

@@ -58,6 +58,9 @@ sudo service sshd reload
 Confirm that SSH is working by removing your user's SSH key in the UI, adding a
 new one, and attempting to pull a repo.
 
+> **Note:** For Omnibus Docker, `AuthorizedKeysCommand` is setup by default in
+GitLab 11.11 and later.
+
 > **Warning:** Do not disable writes until SSH is confirmed to be working
 perfectly, because the file will quickly become out-of-date.