prevent mess when copying BaseObject instances

Note: to understand this fix, see AbstractElement.__init__ -- it calls
deepcopy on parent.env, it caused copying of objects we do not want to
copy such as thread locks.

weboob/capabilities/base.py

@@ -338,6 +338,9 @@ class BaseObject(object):
         obj._fields = copy(self._fields)
         return obj
 
+    def __deepcopy__(self, memo):
+        return self.copy()
+
     def set_empty_fields(self, value, excepts=()):
         """
         Set the same value on all empty fields.