Background: In Mininet 2.2, waitConnected() waits forever
by default. We are going to preserve this behavior for 2.3.
Therefore, the --wait/-w option will wait forever. This is used
in the tests to make sure that all switches have connected to
their controllers.
A new --twait/-t <int> option has been added for timed waits.
The API for Mininet(....waitConnected=False/True) is preserved,
but you can now pass in an integer wait time. False means
do not wait at all. True means wait forever. I have elected
for now to preserve None also meaning wait forever as it was
in 2.2, but note that you should probably use the boolean
True/False instead.