A test which connects 256 switches.

Then checks if they are present
in /restconf/operational/network-topology:network-topology/topology/flow:1
This test does not affect integration process.

Change-Id: I3cc5446b5a636d252a0021ae714c49c7d4e7c5b3
Signed-off-by: Peter Gubka <pgubka@cisco.com>