Configure a dedicated syslog file for carp-ovh logs

Summary:
This change adds:

• a dedicated log file at /var/log/carp.log
• a syslog configuration file in /usr/local/etc/syslog.d/carp.conf to redirect carp-ovh logs to /var/log/carp.log
• a newsyslog configuration file in /etc/newsyslog.conf.d/carp.conf to rotate and compress carp log files

Ref T2292

Test Plan:

• salt 'router-003' state.apply roles/router
• salt 'router-002' state.apply roles/router
• Restart syslogd
• Simulate failover
• Verify the logs for carp-ovh is written to /var/log/carp.log with tail -f /var/log/carp.log

Reviewers: dereckson, Duranzed

Reviewed By: dereckson

Subscribers: Duranzed, dereckson

Maniphest Tasks: T2292

Differential Revision: https://devcentral.nasqueron.org/D4036