Reorg tests setup and add teardown/cleanup

Perform clean up at the end of the tests. Also reorganized
setup/teardown in env_* files in a similar way proposed in dnsrecord
module.

tests/dnszone/test_dnszone.yml

@@ -7,11 +7,8 @@
   tasks:
 
   # Setup
-  - name: Ensure zone is absent.
-    ipadnszone:
-      ipaadmin_password: SomeADMINpassword
-      name: testzone.local
-      state: absent
+  - name: Setup testing environment
+    include_tasks: env_setup.yml
 
   # Tests
   - name: Ensure zone is present.
@@ -186,3 +183,7 @@
       state: absent
     register: result
     failed_when: result.changed
+
+  # Teardown
+  - name: Teardown testing environment
+    include_tasks: env_teardown.yml