repmgrd: add configuration file parameter "standby_reconnect_timeout"

This is used for determining a timeout when reconnecting to the standby
after executing the "follow_command". This will normally not need to be
set explicitly, but maybe useful in cases where the standby's startup
phase can last longer than usual.

repmgr.h

@@ -77,6 +77,9 @@
 #define DEFAULT_REPLICATION_LAG_CRITICAL     600 /* seconds */
 #define DEFAULT_WITNESS_SYNC_INTERVAL        15  /* seconds */
 #define DEFAULT_WAIT_START                   30  /* seconds */
+#define DEFAULT_PROMOTE_CHECK_TIMEOUT        60  /* seconds */
+#define DEFAULT_PROMOTE_CHECK_INTERVAL       1   /* seconds */
+#define DEFAULT_STANDBY_RECONNECT_TIMEOUT    60  /* seconds */
 
 #ifndef RECOVERY_COMMAND_FILE
 #define RECOVERY_COMMAND_FILE "recovery.conf"