In QoS devref, replace neutron.extensions.qos.VALID_RULE_TYPES by
neutron.services.qos.qos_consts.VALID_RULE_TYPES.
Change-Id: Id98b906733fd44bb03da2b38f3bb9a9e35174bfc
Any plugin or Ml2 mechanism driver can claim support for some QoS rule types by
providing a plugin/driver class property called 'supported_qos_rule_types' that
should return a list of strings that correspond to QoS rule types (for the list
-of all rule types, see: neutron.extensions.qos.VALID_RULE_TYPES).
+of all rule types, see: neutron.services.qos.qos_consts.VALID_RULE_TYPES).
In the most simple case, the property can be represented by a simple Python
list defined on the class.