prometheus: Fix "cli configuration" changes not taking effect automatically

Fixes: bd19c007 ("Add configuration to retain prometheus data for 1 year")

roles/prometheus/handlers/main.yml

 - name: Reload prometheus
   service: name=prometheus state=reloaded
+
+- name: Restart prometheus
+  service: name=prometheus state=restarted

roles/prometheus/tasks/main.yml

@@ -7,7 +7,7 @@
 
 - name: Install prometheus cli configuration
   template: src=prometheus.conf.j2 dest=/etc/conf.d/prometheus owner=root group=root mode=644
-  notify: Reload prometheus
+  notify: Restart prometheus
 
 - name: Install prometheus web-config configuration
   template: src=web-config.yml.j2 dest=/etc/prometheus/web-config.yml owner=root group=prometheus mode=640