fix(health): used_swap alarm calc (#11868)

health/health.d/swap.conf

@@ -25,7 +25,7 @@ component: Memory
 component: Memory
        os: linux freebsd
     hosts: *
-     calc: ($used + $free) > 0 ? ($used * 100 / ($used + $free)) : 0
+     calc: (($used + $free) > 0) ? ($used * 100 / ($used + $free)) : 0
     units: %
     every: 10s
      warn: $this > (($status >= $WARNING)  ? (80) : (90))