Add connection manager to Openstack_Neutron test suite.

Add connection manager to Openstack_Neutron test suite.

This robot file setup the connection between OVS and ODL.
It also verifie the connection is correctly set up, and
flows are correctly pushed to the OVS instance, creating a bridge,
a port and an interface.

Patch Set 1: Initial commit
Patch Set 2: Remove whitespaces
Patch Set 3: Remove useless library, setup and teardown. Also update tests documentation
Patch Set 4; Rebase and clean

Change-Id: I17055fab4a65ff86f419fac29f84a241edd52ce7
Signed-off-by: Alexis de Talhouët <adetalhouet@inocybe.com>