Rather than simply emit "FAILED" for an unreachable node,
indicate whether its state matches that expected by repmgr.
E.g. following output:
ID | Name | Role | Status | Upstream | Connection string
----+-------+---------+----------------------+----------+----------------------------------------------------
1 | node1 | primary | * running | | host=localhost dbname=repmgr user=repmgr port=5501
2 | node2 | standby | ? unreachable | node1 | host=localhost dbname=repmgr user=repmgr port=5502
3 | node3 | standby | ! running as primary | node1 | host=localhost dbname=repmgr user=repmgr port=5503
is for a cluster where "node2" has been manually stopped, and "node3"
manually promoted.
