#108 Support for local HTTP server

[scbjans]

fix #108

If the http_directory key is set in the Packer template an HTTP server is started, which is accessible by the created VM.
The IP address on which the HTTP server is started is determined as the first non-loopback interface IP address; if needed this can be overridden by setting the http_ip key in the Packer template.

[scbjans]

@mkuzmin could you please review this as PR for #108

[mkuzmin]

Thank you!

[mkuzmin]

I’ll quote my comment from #108 (comment) here:

But I would still prefer floppy approach if possible.
HTTP connection is easy in VirtualBox when Packer and VM are within localhost.

Our scenario is remote, and there are multiple issues:

• Desktop firewall can block incoming connections to Packer process.
• Using Docker containers, Packer is put behind NAT. You can configure port forwarding, but then you have to explicitly announce its IP address.
• When Packer machine has multiple network interfaces, the wrong one may be selected. This could be improved, but requires even more logic.