Double quotation mark within double quoted string value

[blurrcat]

The value of parameter line in the lineinfile task contains double quotation marks. In Ansible 2, it complains:

ERROR! this task 'lineinfile' has extra params, which is only allowed in the following modules: command, shell, script, include, include_vars, add_host, group_by, set_fact, raw, meta

The error appears to have been in '/Users/harry/workspace/ansible_roles/mongo_mongod/tasks/main.yml': line 35, column 3, but may
be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:

    tasks:
      - name: make sure the hostname is available in /etc/hosts
        ^ here

Changing them to single quotation marks. Also add basic tests.