openflow_input: fix of_group_desc_stats_entry.group_type

use enum ofp_group_type for consistency with the group_mod messages
Merge branch 'master' of github.com:floodlight/loxigen
Merge branch 'master' of github.com:floodlight/loxigen
loxi_ir: minor fix for compability with python <2.7.3

In python <2.7.3, vars() of a namedtuple returns a TypeError.
Using _asdict instead.
Merge branch 'master' of github.com:floodlight/loxigen
Merge into master from pull request #132:
openflow_input: fix of_group_desc_stats_entry.group_type (https://github.com/floodlight/loxigen/pull/132)