Updates playbooks with new OSSEC role logic

We've consolidated the "ossec-agent" and "ossec-server" roles into
"ossec", and excised the postfix logic from the "ossec-server" role into
a discrete "postfix" role. Playbooks must have these updated
accordingly.

We're nearly at the point where we can standardize on a single playbook
for prod and staging. Onward!

(cherry picked from commit 77af2f2)

install_files/ansible-base/securedrop-prod.yml

@@ -15,16 +15,23 @@
     - { role: tor-hidden-services, tags: tor }
   become: yes
 
-- name: Configure SecureDrop Monitor Server.
+- name: Configure mailing utilities.
   hosts: securedrop_monitor_server
   roles:
-    - { role: ossec-server, tags: [ ossec, ossec_server ] }
+    - role: postfix
+      tags: postfix
+  become: yes
+
+- name: Configure OSSEC.
+  hosts: securedrop
+  roles:
+    - role: ossec
+      tags: ossec
   become: yes
 
 - name: Configure SecureDrop Application Server.
   hosts: securedrop_application_server
   roles:
-    - { role: ossec-agent, tags: [ ossec, ossec_agent ] }
     - { role: app, tags: app }
   become: yes
 

install_files/ansible-base/securedrop-staging.yml

@@ -31,16 +31,23 @@
         when: install_local_packages }
   become: yes
 
-- name: Configure OSSEC manager.
+- name: Configure mailing utilities.
   hosts: mon-staging
   roles:
-    - { role: ossec-server, tags: [ ossec, ossec_server ] }
+    - role: postfix
+      tags: postfix
+  become: yes
+
+- name: Configure OSSEC.
+  hosts: staging
+  roles:
+    - role: ossec
+      tags: ossec
   become: yes
 
 - name: Configure SecureDrop Application Server.
   hosts: app-staging
   roles:
-    - { role: ossec-agent, tags: [ ossec, ossec_agent ] }
     - { role: app, tags: app }
     - { role: app-test, tags: app-test }
   become: yes