[Watchdog] Longer sleep for open relay check

data/Dockerfiles/watchdog/watchdog.sh

@@ -210,7 +210,7 @@ external_checks() {
       sleep 60
     else
       diff_c=0
-      sleep $(( ( RANDOM % 20 ) + 120 ))
+      sleep $(( ( RANDOM % 20 ) + 1800 ))
     fi
   done
   return 1