one-templates: when HTTP thread crash the runner is stuck

During my tests, I had a crash of the one-templates tool:

==> gitlab-runner.qemu.freebsd (shell-local): #<Thread:0x000056121752b9b0 /home/gitlab-runner/builds/UpbGXxc7/0/daniel.dehennin/builder/tools/one-templates:157 run> terminated with exception (report_on_exception is true):
==> gitlab-runner.qemu.freebsd (shell-local): /home/gitlab-runner/builds/UpbGXxc7/0/daniel.dehennin/builder/tools/one-templates:204:in `block in publishImage': [one.image.allocate] Cannot parse image SIZE: Failed to get image head (Exception)

It stayed stuck until I restarted the gitlab-runner service manually for that runner (I didn't wanted to wait for the 1h timeout).

I think we should take more precaution in case of a crash to terminate the process with an exit value.