add OF 1.3 flow_stats test module
flow_stats-1.3: add a test for matching on cookie
flow_stats.CookieFlowStats: include random cookies/masks
flow_stats.CookieFlowStats: use iteritems
flow_stats.CookieFlowStats: rearrange "matches" for loops
Merge into master from pull request #72:
OF 1.3 flow stats tests (https://github.com/floodlight/oftest/pull/72)