stack/slapos: Upgrade the version of setuptools

Otherwise setup_requires in python-dateutil trying to install
the latest version of setuptools_scm and it does not support python2.7.
As the result, fails to install it.

---

INFO networkcache: Downloading pypi-index-96af89cdde216340df5aec1e9a1392e0-python-dateutil==2.7.3...
INFO networkcache: ignored unhandled exception at /srv/slapgrid/slappart6/srv/testnode/dcj/soft/beff23aad53b201b191f995a667eb5f9/eggs/slapos.libnetworkcache-0.15-py2.7.egg/slapos/networkcachehelper.py:106
INFO HTTPError: HTTP Error 404: Not Found
INFO networkcache: Downloading pypi-index-99e2b3234a294248d07c2bb8e6698302-python-dateutil==2.7.3...
INFO networkcache: ignored unhandled exception at /srv/slapgrid/slappart6/srv/testnode/dcj/soft/beff23aad53b201b191f995a667eb5f9/eggs/slapos.libnetworkcache-0.15-py2.7.egg/slapos/networkcachehelper.py:106
INFO HTTPError: HTTP Error 404: Not Found
INFO networkcache: Downloading pypi-index-a46be9bd3756ada5c303353adbb6407f-python-dateutil==2.7.3...
INFO Downloaded http://www.nexedi.org/static/packages/source/slapos.buildout/ from network cache.
INFO networkcache: Downloading pypi-index-23ce7712b6e6cbc7d09787f73e5c3dc5-python-dateutil==2.7.3...
INFO Downloaded https://pypi.org/simple/python-dateutil/ from network cache.
INFO networkcache: Downloading slapos-buildout-a35382ef8370ced1c46d97632a2ec508...
INFO Downloaded https://files.pythonhosted.org/packages/a0/b0/a4e3241d2dee665fea11baec21389aec6886655cd4db7647ddf96c3fad15/python-dateutil-2.7.3.tar.gz#sha256=e27001de32f627c22380a688bcc43ce83504a7bc5da472209b4c70f02829f0b8 from network cache.
INFO Couldn't find index page for 'setuptools_scm' (maybe misspelled?)
INFO No local packages or working download links found for setuptools_scm
INFO error: Could not find suitable distribution for Requirement.parse('setuptools_scm')
INFO An error occurred when trying to install python-dateutil 2.7.3. Look above this message for any errors that were output by easy_install.
INFO While:
INFO   Installing neoppod.
INFO Error: Couldn't install: python-dateutil 2.7.3
ERROR Failed to run buildout profile in directory '/srv/slapgrid/slappart6/srv/testnode/dcj/soft/beff23aad53b201b191f995a667eb5f9'
INFO Finished software releases.

stack/slapos.cfg

@@ -104,7 +104,7 @@ egg = ${:_buildout_section_name_}
 setup-eggs = setuptools_scm
 
 [versions]
-setuptools = 33.1.1
+setuptools = 44.1.1
 # Use SlapOS patched zc.buildout
 zc.buildout = 2.5.2+slapos013
 # Use SlapOS patched zc.recipe.egg (zc.recipe.egg 2.x is for Buildout 2)
@@ -255,6 +255,10 @@ uritemplate = 3.0.0
 # slapos.core==1.4.8
 zope.interface = 4.3.3
 
+# Required by:
+# python-dateutil 2.7.3
+setuptools-scm = 5.0.0
+
 [networkcache]
 download-cache-url = http://download.shacache.org/
 download-dir-url = http://dir.shacache.org/