Fix cosmetic problems in YAML source

This change corrects problems reported by the `yamllint` linter.

Since key duplication problems were removed in 4d48711, this commit
mainly fixes trailing spaces and extra empty lines at beginning/end of
files.

test/integration/targets/includes/test_includes2.yml

@@ -1,8 +1,7 @@
-
 - name: verify playbook includes can take parameters
   hosts: testhost
   tasks:
-    - assert: 
+    - assert:
         that:
           - "parameter1 == 'asdf'"
           - "parameter2 == 'jkl'"
@@ -10,7 +9,7 @@
 - name: verify task include logic
   hosts: testhost
   gather_facts: True
-  roles: 
+  roles:
     - { role: test_includes, tags: test_includes }
   tasks:
     - include: roles/test_includes/tasks/not_a_role_task.yml