This should replace the autoscale of runners that spawn between 1 and
10 machines to have 10 machine always running. (But will start with 1
as the autoscaling didn't work for other reason.)

We remove docker+machine stuff as we will use "docker" on the machine
setup by teraform. (docker+machine is mainly use for autoscaling.)

This is to workaround "jobs" which fails with `git clone` error for
example:
    Cloning into 'qemu-xen-dir-remote.tmp'...
    error: inflate: data stream error (incorrect data check)
    fatal: serious inflate inconsistency
    fatal: index-pack failed

For the renamed "gitlab-docker-machine" to "gitlab-docker", we can't
really use "count" to increase the number of instance or they would
all have the same name. Instead, we add cound to "random_pet.name" and
create an instance for each one of the pet name.

We now provide a name to `gitlab-runner register` via --name so we can
reference to it to unregister it.