Fix existing OpenFlow 1.2 testcases

Reviewer: @andi-bigswitch
CC 

These tests were broken when we replaced pylibopenflow with pyloxi. Most of these changes are mechanical, adapting the tests to the pyloxi API. The commit "parse: support OF 1.2" is the only one that needs careful review.

The tests pass against of12softswitch after fixing a couple of bugs in the switch.