[Buildbot] #2937: Modernize Dockerfile

[Buildbot trac]

#2937: Modernize Dockerfile
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Reporter:  Quentin  |      Owner:
    Type:  defect   |     Status:  new
Priority:  major    |  Milestone:  undecided
 Version:  master   |   Keywords:
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 Docker has evolved quite quickly before reaching 1.0, and the Dockerfile
 in master/contrib/Dockerfile is no longer following best practices.
 According to GitHub discussions, it:

  * does not publish master's web status port (8010)
  * creates an ssh service (omg this is so 2013!)
  * does not expose the config in a separated volume
  * uses echo > /path/to/config instead of ADD command
  * hardcodes the password

 Someone should read the current Docker docs and come up with a better
 solution. It looks like tardyp will be able to review it.

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Ticket URL: <http://trac.buildbot.net/ticket/2937>
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