There are three modifications in 'ovxctl.py'. Fix two functions, 'pa_startPort' and 'pa_stopPort', which miss the '<virtual_port>' describtion in parameter 'usage'. And replace 'hostId' by 'portId' in the if statememt of the fucntion 'do_startPort'.

Change-Id: I4ca0654469431008ce9c2ead62b40813e2228cae