Create a check before creating a default route on RouterOS

https://github.com/anthr76/infra/blob/0562cba749d0d24b59efd3f81410620e4d7b89e7/ansible/nwk1-sw-core.yaml#L47

Currently RouterOS does not check if an existing route exists so adding it in its current context will continually adding it. Update this playbook to ensure that multiple same routes are created.