Missing filebeats config results in service startup failure

geerlingguy-filebeat role defaults the filebeats `certificate_authorities` property to `${filebeat_ssl_certs_dir}` if the `${filebeat_ssl_ca_file}` property is not provided to ansible.

https://github.com/geerlingguy/ansible-role-filebeat/blob/master/templates/filebeat.yml.j2#L67

This results in a startup failure on both the logs and web servers.

```
2024-03-25T03:18:08.764Z INFO instance/beat.go:292 Setup Beat: filebeat; Version: 7.17.18
2024-03-25T03:18:08.764Z WARN [cfgwarn] tlscommon/config.go:100 DEPRECATED: Treating the CommonName field on X.509 certificates as a host name when no Subject Alternative Names are present is going to be removed. Please update your certificates if needed. Will be removed in version: 8.0.0
2024-03-25T03:18:08.764Z ERROR [tls] tlscommon/tls.go:162 Failed reading CA certificate: read /etc/pki/logstash/: is a directory
2024-03-25T03:18:08.765Z INFO instance/beat.go:426 filebeat stopped.
2024-03-25T03:18:08.765Z ERROR instance/beat.go:1027 Exiting: error initializing publisher: 1 error: read /etc/pki/logstash/: is a directory reading /etc/pki/logstash/
Exiting: error initializing publisher: 1 error: read /etc/pki/logstash/: is a directory reading /etc/pki/logstash/
```

Suggested fix is to add the `filebeat_ssl_ca_file` property to the vars files for both web and elk.

```
...
filebeat_ssl_ca_file: elk-example.crt
```

Review the filebeat.yml.j2 template at the linked line and the vars files for the web and elk servers. Confirm how the missing filebeat_ssl_ca_file produces the directory path, then add the property in both relevant vars files and verify that the generated configuration points to the intended certificate file.

Written by the indexing model from the issue text.