zram-generator: use systemd-zram-setup@zram0 handler

Restarting swap.target doesn't apply configuration changes; instead we
can restart systemd-zram-setup@zram0 which seems to do what we wanted.

roles/common/handlers/main.yml

@@ -19,5 +19,5 @@
 - name: restart syslog-ng
   service: name=syslog-ng@default state=restarted
 
-- name: restart swap.target
-  service: name=swap.target state=restarted daemon_reload=yes
+- name: restart systemd-zram-setup@zram0
+  service: name=systemd-zram-setup@zram0 state=restarted daemon_reload=yes

roles/common/tasks/main.yml

@@ -141,7 +141,7 @@
 - name: install zram-generator config for zram
   copy: src=zram-generator.conf dest=/etc/systemd/zram-generator.conf owner=root group=root mode=0644
   notify:
-    - restart swap.target
+    - restart systemd-zram-setup@zram0
   when: enable_zram_swap
 
 - name: start systemd-oomd