This is a follow-up of commit 6f009a9f

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'

This reverts commit b3c5f181.

Maybe we should use 'parts +=' everywhere in /components/*/buildout.cfg

When looking for emergency user, zope configuration is not fully loaded
yet, thus if we do not set INSTANCE_HOME at startup, it will be wrong.
With this change, setting an "access" file under erp5shared folder will
work properly

In the same time, fix HOME folder to not be in a tmp folder

When looking for emergency user, zope configuration is not fully loaded
yet, thus if we do not set INSTANCE_HOME at startup, it will be wrong.
With this change, setting an "access" file under erp5shared folder will
work properly

In the same time, fix HOME folder to not be in a tmp folder

Add support for "hosts" aliasing in Zope instances.
Add support for SASL relayhost with mandatory TLS encryption.
Add mandatory TSL + SASL authentication, to not be an open relay.
Wrap postfix commands with proper environment instead of symlink +
source-able script.
Add ipv6 listening support (untested).
Drop non-required main.cf configuration options.
Make postifx instance optional (requires postmaster address to be
provided).
Document and rework smtp-related parameters.
Expose an userhosts hostname for smtp server.
Add diversion support (solution to "prod clone sent mails to real customer").
Use etc/run rather than etc/service, for consistency (if it needs to be
changed, it must be changed for all software types).
Hook into syslog and setup local syslog daemon, with logrotate integration.
Update TODO entries.