def build_host_string(container, docker_host_string):
ip = docker_ip(docker_host_string)<EOL>host_string = "<STR_LIT>" % (ip,<EOL>docker_container_port(container))<EOL>return host_string<EOL>
builds a fabric ssh host string for a docker container

params:
    string container: docker instance id
    string docker_host_string: URL for the docker daemon

returns:
    string: < root@docker_ip_address:port_number >