_start_run_deps is broken due to changes in DockerInstance

[dor-zusman]

In previous commits a support for receiving (workspace_hex, delegated_volume, user) in __init__ was added to DockerInstance, while the instantiation code inside _start_run_deps does not pass these variables.
This in turn causes dazel installation to fail.
The relevant code is inside dazel.py:

class DockerInstance:
    """Manages communication and runs commands on associated docker container.
    A DockerInstance can build the image for the container if necessary, run it,
    set it up through configuration variables, and pass on commands to it.
    It streams the output directly and blocks until the command finishes.
    """

    def __init__(self, instance_name, image_name, run_command, docker_command, dockerfile,
                       repository, directory, command, volumes, ports, network,
                       run_deps, docker_compose_file, docker_compose_command,
                       docker_compose_project_name, docker_compose_services, bazel_user_output_root,
                       bazel_rc_file, docker_run_privileged, docker_machine, dazel_run_file,
                       workspace_hex, delegated_volume, user):

and

def _start_run_deps(self):
        """Starts the containers that are marked as runtime dependencies."""
        for (run_dep_image, run_dep_name) in self.run_deps:
            run_dep_instance = DockerInstance(
                instance_name=run_dep_name,
                image_name=run_dep_image,
                run_command=None,
                docker_command=None,
                dockerfile=None,
                repository=None,
                directory=None,
                command=None,
                volumes=None,
                ports=None,
                network=self.network,
                run_deps=None,
                docker_compose_file=None,
                docker_compose_command=None,
                docker_compose_project_name=None,
                docker_compose_services=None,
                bazel_rc_file=None,
                bazel_user_output_root=None,
                docker_run_privileged=self.docker_run_privileged,
                docker_machine=self.docker_machine,
                dazel_run_file=None)

[barakh]

There is a workaround for that..

1. Edit /usr/local/bin/dazel to use python3 instead of the deafult python(which is 2.7 for ubuntu):
   #!/usr/bin/python3
2. Install docker compose - preventing the faulty flow