This will cover both the case when an entire node including
repmgrd goes down, and when one PostgreSQL instance goes down
but repmgrd is still up (in which case only one of the repmgrds
will handle the failover).
When creating recovery.conf outside of "repmgr standby clone",
there was no way of knowing if a replication user had been
explicitly provided with --replication-user, meaning the value
of "primary_conninfo" would be set to the "conninfo" field of the
node's upstream node record.
We'll add an extra column to store the replication user for each
node so it can be referenced at any time.
