Ensuring ssh key.pub is set to default perms

What does this MR do?

During a customer support is was noted that following https://docs.gitlab.com/ee/administration/geo/replication/configuration.html#step-2-manually-replicate-the-primary-sites-ssh-host-keys will change the default permissions of the ssh public keys from 0644 -> 0600

This MR is to ensure that these are kept at the default permission.

Example (default permissions)

# ls -l /etc/ssh/ssh_host_*_key*
-rw------- 1 root root 1393 Mar  9 08:46 /etc/ssh/ssh_host_dsa_key
-rw-r--r-- 1 root root  612 Mar  9 08:46 /etc/ssh/ssh_host_dsa_key.pub
-rw------- 1 root root  513 Mar  9 08:46 /etc/ssh/ssh_host_ecdsa_key
-rw-r--r-- 1 root root  184 Mar  9 08:46 /etc/ssh/ssh_host_ecdsa_key.pub
-rw------- 1 root root  419 Mar  9 08:46 /etc/ssh/ssh_host_ed25519_key
-rw-r--r-- 1 root root  104 Mar  9 08:46 /etc/ssh/ssh_host_ed25519_key.pub
-rw------- 1 root root 2610 Mar  9 08:46 /etc/ssh/ssh_host_rsa_key
-rw-r--r-- 1 root root  576 Mar  9 08:46 /etc/ssh/ssh_host_rsa_key.pub

Related issues

Customer ZD - internal link only.

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