Add java headless as a valid deb dependency

[theHilikus]

For systems that have a headless version of the jre installed such as openjdk-8-jre-headless

Motivation Allow installation of deb package in systems with a headless jre

Changes Add extra dependency option

[cla-bot[bot]]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have the users @theHilikus on file. In order for us to review and merge your code, please sign our Contributor License Agreement to get yourself added. You'll find the CLA and more information here: https://github.com/hivemq/hivemq-community/blob/master/CONTRIBUTING.adoc#contributor-license-agreement

[gitseti]

Hey @theHilikus and thank you for the PR. You would need to sign our CLA as stated above so that we can merge this PR:

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have the users @theHilikus on file. In order for us to review and merge your code, please sign our Contributor License Agreement to get yourself added. You'll find the CLA and more information here: hivemq/hivemq-community@master/CONTRIBUTING.adoc#contributor-license-agreement