fixup! stack/erp5 += WCFS service (technology preview)

In commit 48b24182 I passed 'wcfs_enable' to instance-zope.cfg as string
instead of an object. As the result, even if it was wcfs_enable=False, in
instance-zope.cfg in

    ---- 8< ---- https://lab.nexedi.com/nexedi/slapos/blob/8d3af101/stack/erp5/instance-zope.cfg.in#L68-72)
    {% if slapparameter_dict['wcfs_enable'] %}
      WENDELIN_CORE_VIRTMEM=r:wcfs+w:uvmm
    {% else %}
      WENDELIN_CORE_VIRTMEM=rw:uvmm
    {% endif %}

it was always taking the first branch, becuse slapparameter_dict['wcfs_enable']
was giving 'False' - a string - whose boolean value is True

    In [1]: bool('False')
    Out[1]: True

-> Fix it by passing slapparameter_dict['wcfs_enable'], similarly to most other
keys, as object.

stack/erp5/buildout.hash.cfg

@@ -74,7 +74,7 @@ md5sum = 8bd7f89b7c1e453ecc952659a01347e6
 
 [template-erp5]
 filename = instance-erp5.cfg.in
-md5sum = aea5ab7b58beae9ada8b14f1c548e493
+md5sum = f33e82cb68924decb77142b79dce4fab
 
 [template-zeo]
 filename = instance-zeo.cfg.in

stack/erp5/instance-erp5.cfg.in

@@ -259,7 +259,7 @@ config-wendelin-core-zblk-fmt = {{ dumps(slapparameter_dict.get('wendelin-core-z
 config-wsgi = {{ dumps(slapparameter_dict.get('wsgi', True)) }}
 config-test-runner-enabled = {{ dumps(test_runner_enabled) }}
 config-test-runner-node-count = {{ dumps(test_runner_node_count) }}
-config-wcfs_enable = {{ wcfs_enable }}
+config-wcfs_enable = {{ dumps(wcfs_enable) }}
 software-type = zope
 
 {% set global_publisher_timeout = slapparameter_dict.get('publisher-timeout') -%}