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/postgresql/defaults/main.yml

@@ -5,4 +5,3 @@ db_user1: 'ansible_db_user1'
 db_user2: 'ansible_db_user2'
 
 tmp_dir: '/tmp'
-