repmgrd: improve handling of "degraded monitoring"

In some cases, the monitored upstream may not be available for a while
(e.g. network split), in which case it makes sense to have repmgrd
keep running and trying to reconnect. Previously it would just keel
over and quit.

repmgr.conf.sample

@@ -180,6 +180,10 @@ ssh_options=''                            # Options to append to "ssh"
 
 #monitoring_history=no
 
+#degraded_monitoring_timeout=-1         # Interval (in seconds) after which repmgrd
+                                        # will terminate if the server being monitored
+                                        # is no longer available. -1 (default)
+                                        # disables completely.
 
 #------------------------------------------------------------------------------
 # service control commands