[FIX] sql_db: connection pool created lazily.

- This is necessary to give a chance to change the config just after importing openerp.

bzr revid: vmt@openerp.com-20110421103125-3lv609wnu3vh2m4f

openerp/sql_db.py

@@ -374,9 +374,12 @@ def dsn_are_equals(first, second):
     return key(first) == key(second)
 
 
-_Pool = ConnectionPool(int(tools.config['db_maxconn']))
+_Pool = None
 
 def db_connect(db_name):
+    global _Pool
+    if _Pool is None:
+        _Pool = ConnectionPool(int(tools.config['db_maxconn']))
     currentThread().dbname = db_name
     return Connection(_Pool, db_name)