In particular, if running "repmgr cluster show" against a database
without the repmgr metadata, showing the error (rather than just
"no records found" etc.) will provide some clues about the problem.
Previously, if an issue was encountered with the old primary, but user
provided -F/--force to have repmgr promote the standby anyway, repmgr
would exit with the log message "STANDBY SWITCHOVER is complete"
and exit code 0 (SUCCESS).
To better report this partial completion, repmgr will now emit the message
"STANDBY SWITCHOVER has completed with issues" (and a HINT to check preceding
log messages) and new exit code 22 (ERR_SWITCHOVER_INCOMPLETE).
