usg remediation for chrony rule 2.3.3.2: Missing trailing new line

[Gaetan Gouzi]

- Version: Ubuntu 22.04.4 LTS Jammy + usg 22.04.6
- NTP charm: 4.2 latest/stable rev 50
- Context: Applying cis_level1 hardening on units with ntp-charm subordinate
- Problem: NTP unit blocked after reboot `chrony: Not running`
- Debugging: `Fatal error : Too many arguments for include directive at line 45 in file /etc/chrony/chrony.conf`

Indeed the line in `/etc/chrony/chrony.conf` looks like
```
include /etc/chrony/conf.d/*.confuser _chrony`
```

Whereas the same line look like this on a non-hardened unit:
```
include /etc/chrony/conf.d/*.conf
```

We suspect the CIS rule `2.3.3.2 Ensure chrony is running as user _chrony (Automated)` remediation script is defective. CIS documentation mentioned the following for this rule:

```
Remediation:
Add or edit the user line to /etc/chrony/chrony.conf or a file ending in .conf in
/etc/chrony/conf.d/:
user _chrony
```

Configuration should ideally look like this:
```
include /etc/chrony/conf.d/*.conf
user _chrony
```

If we manually fix it, NTP charm becomes active/idle.
We suspect we are missing a trailing new line upon appending `user _chrony` to the `/etc/chrony/chrony.conf`.

The ntp-charm seems to replace the chrony configuration with a template: https://git.launchpad.net/ntp-charm/tree/templates/chrony.conf where the trailing new line gets stripped.