Fix config file dependency issue

Without this patch, I get this error on the first run:

```
Error: Could not set 'present' on ensure: No such file or directory - /etc/logstashforwarder/config.json at 131:/etc/puppet/puppet-scripts/modules/logstashforwarder/manifests/config.pp
Error: Could not set 'present' on ensure: No such file or directory - /etc/logstashforwarder/config.json at 131:/etc/puppet/puppet-scripts/modules/logstashforwarder/manifests/config.pp
Wrapped exception:
No such file or directory - /etc/logstashforwarder/config.json
Error: /Stage[main]/Logstashforwarder::Config/Logstashforwarder_config[lsf-config]/ensure: change from absent to present failed: Could not set 'present' on ensure: No such file or directory - /etc/logstashforwarder/config.json at 131:/etc/puppet/puppet-scripts/modules/logstashforwarder/manifests/config.pp
Notice: /Stage[main]/Logstashforwarder::Config/File[/etc/logstashforwarder]/ensure: created
Notice: /Stage[main]/Logstashforwarder::Config/File[/etc/logstashforwarder/ssl]/ensure: created
```