Report swap metrics in bytes

Change-Id: Ic39fa0f18e0d9aeca0ef73ae6d985d12d15a1c3a

linux/files/collectd_swap.conf

+<LoadPlugin swap>
+  Globals false
+</LoadPlugin>
+
+<Plugin swap>
+  ReportBytes {{ plugin.get('report_bytes', False)|lower }}
+</Plugin>
+

linux/meta/collectd.yml

     ignore_selected: True
   linux_storage_swap:
     plugin: swap
+    template: linux/files/collectd_swap.conf
+    report_bytes: True