Revert "turn off check swap if needed"

This reverts commit a63f4053f3.

linux/map.jinja

 {% set storage = salt['grains.filter_by']({
     'Arch': {
         'mount': {},
-        'swap': {
-             'enabled': True,
-         },
+        'swap': {},
         'lvm': {},
         'multipath': {
              'enabled': False,
     },
     'Debian': {
         'mount': {},
-        'swap': {
-             'enabled': True,
-         },
+        'swap': {},
         'lvm': {},
         'multipath': {
              'enabled': False,
     },
     'RedHat': {
         'mount': {},
-        'swap': {
-             'enabled': True,
-         },
+        'swap': {},
         'lvm': {},
         'multipath': {
              'enabled': False,

linux/meta/sensu.yml

     occurrences: 1
     subscribers:
     - local-linux-system
-{%- if storage.swap.enabled %}
+{%- if storage.swap is defined %}
   local_linux_storage_swap_usage_{{ system.name|replace('.', '-') }}-{{ system.domain|replace('.', '-') }}:
     command: "PATH=$PATH:/usr/lib64/nagios/plugins:/usr/lib/nagios/plugins check_swap -a -w 50% -c 20%"
     interval: 60