Conflicts:
	stack/slapos.cfg

Zope integrated Products.signalstack back in 2010:

    https://github.com/zopefoundation/Zope/commit/16796274
    ( Integrated the Products.signalstack / z3c.deadlockdebugger
      packages. You can now send a SIGUSR1 signal to a Zope process and get a
      stack trace of all threads printed out on the console. This works even
      if all threads are stuck. )

In 404150b7 (wendelin: Teach -dev build to dump all threads traceback on
SIGUSR1) it was my mistake to add Products.signalstack.

/reviewed-by TrustMe
/cc @Tyagov

This fixes the following random failures:

While:
  Installing slapos-deps-eggs.
  Getting distribution for 'ZODB3==3.10.5+SlapOSPatched001'.

An internal error occurred due to a bug in either zc.buildout or in a
recipe being used:
Traceback (most recent call last):
  ...
  File "zc/buildout/easy_install.py", line 968, in _get_dist
    shutil.copytree(dist.location, newloc)
  File "shutil.py", line 177, in copytree
    os.makedirs(dst)
  File "os.py", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 17] File exists: '.../eggs/ZODB3-3.10.5-py2.7-linux-x86_64.egg'

* kirrlab/x/gitlab:
  .

* master: (45 commits)
  add firewalld component
  fixup! NEO: fix build of [slapos-deps-eggs]
  version up : mesa 11.0.3.
  version up eggs.
  python: Add patch to support pytracemalloc and add the corresponding egg to ERP5.
  NEO: do not rely on $HOME, which is not always equal to ${buildout:directory}
  NEO: fix build of [slapos-deps-eggs]
  component python-setuptools updated to version 18.4
  use lockfile egg version 0.10.2 for kvm and webrunner development
  monitor2: fix rss link
  monitor2: add minimal css for the default promise interface
  monitor2: add rss button
  version up: numpy 1.10.0.post2.
  monitor2: add rss feed
  version up : zc.buildout 1.7.1.post13 and zc.recipe.egg 1.3.2.post5.
  version up eggs.
  version up : FreeType 2.6.1.
  version up : pkg-config 0.29
  monitor2: fix status interface js error according to dom
  kvm: cdrom-iso update to version 8.2.0
  ...

By default, this is only true when a partition has a dedicated unix user.
Inside a webrunner, we can have:
  ${buildout:directory} = /srv/slapgrid/slappart0/srv/runner/instance/slappart1
  but $HOME = /srv/slapgrid/slappart0

Zope partitions override HOME as follows:
  home-path = ${buildout:directory}