Geo: Set recovery_target_timeline to latest by default
We needed this setting when a failover happen and the secondary wasn't able to pull the latest segment from the current timeline. Setting to latest allows the secondary to recovery in case this happens.
See https://www.postgresql.org/docs/9.6/static/continuous-archiving.html#BACKUP-TIMELINES for more details.
Relates to gitlab-com/migration#407 (closed)