erp5: Make ZODB pool-size default to thread_amount.

Avoids being spammed with
  WARNING ZODB.DB DB.open() has X open connections with a pool_size of 7
on zopes with more than 7 worker threads.
Also, allows better hit-rate on volatile attributes in such case, as
otherwise connections (and their cache) would be discarded when many
threads would be made busy, decreasing performance.

stack/erp5/buildout.cfg

@@ -341,7 +341,7 @@ md5sum = b0cb0ee97cddc79112a718e065806037
 [template-zope]
 <= download-base
 filename = instance-zope.cfg.in
-md5sum = 144fb4567e12bac2c7ed61e7477d5418
+md5sum = 83304f1940e0d7555bd678e2cea4c738
 link-binary =
   ${aspell:location}/bin/aspell
   ${dmtx-utils:location}/bin/dmtxwrite

stack/erp5/instance-zope.cfg.in

@@ -284,6 +284,7 @@ node-id = {{ dumps(node_id_base ~ '-' ~ index) }}
 {% set log_list = [] -%}
 {% set import_set = set() -%}
 {% for db_name, zodb in zodb_dict.iteritems() -%}
+{%   do zodb.setdefault('pool-size', thread_amount) -%}
 {%   if zodb['type'] == 'neo' -%}
 {%     do import_set.add('neo.client') -%}
 {%     set log = name ~ '-neo-' ~ db_name ~ '.log' -%}