Merge pull request #2825 from dshuvar/dshuvar/docker-options.conf

Changed /etc/systemd/system/docker.service.d/docker-options.conf file for successful parsing mount aguments

roles/docker/templates/docker-options.conf.j2

 [Service]
-Environment="DOCKER_OPTS={{ docker_options | default('') }} \
---iptables=false"
+Environment="DOCKER_OPTS={{ docker_options|default('') }} --iptables=false"
 {% if docker_mount_flags is defined and docker_mount_flags != "" %}
 MountFlags={{ docker_mount_flags }}
 {% endif %}