sw test tool: Add default test files (group)

These test files aim to examine 'group action' of FlowMod message.

Signed-off-by: Yuichi Ito <ito.yuichi0@gmail.com>
sw test tool: group(FF) sample

Signed-off-by: Yuichi Ito <ito.yuichi0@gmail.com>
sw test tool: support fluctuations of sending

Signed-off-by: Yuichi Ito <ito.yuichi0@gmail.com>