BUG-837: IT unstable

IT keep running forever because of change in OFJava + old change in OFPlugin-IT.

- fixed scenario for 2 hello handshake test (OFPluginToLibraryTest)
- fixed threading for scenario execution

Change-Id: I5af8248fd9c92f3bc2e02cac169c4f34599519d7
Signed-off-by: Michal Rehak <mirehak@cisco.com>