[Buildbot] #3166: fix 'buildbot.net' build slave

[Buildbot trac]

#3166: fix 'buildbot.net' build slave
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Reporter:  sa2ajj  |       Owner:
    Type:  task    |      Status:  new
Priority:  major   |   Milestone:  sys - on-bb-infra
 Version:          |  Resolution:
Keywords:          |
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Comment (by sa2ajj):

 Ok, `coverage` is disabled.

 `builds` was fixed (manually):

 * `npm` installed
 * a symlink from `nodejs` to `node` was created (Debian specific thing)
 * builder was updated to use `ftp.int.buildbot.net`
 ([https://github.com/buildbot/metabbotcfg/pull/21 metabbotcfg PR])
 * a key for granting ftp access (`ftp.key`) was created and put to the
 list of authorised keys

 This particular ticket could be closed, but we'll need one for making all
 this part of an ansible playbook.

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Ticket URL: <http://trac.buildbot.net/ticket/3166#comment:5>
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