Fix monasca_checks host_alive YAML configuration

The YAML structure for monasca_checks' host_alive was incorrect in the
playbooks, preventing host_alive checks from functioning.  One would
see no host_alive_status metrics, and this error in collector.log:

.host_alive(services_checks.py:92) | Each service check must have a name

Change-Id: I52a91362d7c958d27087933ccd91de326da9392e

devstack.yml

@@ -18,10 +18,9 @@
           ssh_timeout: 0.5
           ping_timeout: 1
         instances:
-          - mini-mon:
-              name: mini-mon
-              host_name: 192.168.10.4
-              alive_test: ssh
+          - name: mini-mon
+            host_name: 192.168.10.4
+            alive_test: ssh
     keystone_url: http://192.168.10.5:35357/v3
     keystone_admin_token: ADMIN
     keystone_users:

mini-mon.yml

@@ -59,10 +59,9 @@
           ssh_timeout: 0.5
           ping_timeout: 1
         instances:
-          - devstack:
-              name: devstack
-              host_name: 192.168.10.5
-              alive_test: ssh
+          - name: devstack
+            host_name: 192.168.10.5
+            alive_test: ssh
     mysql_host: "{{mini_mon_host}}"
     mysql_users:
       notification: password