test-vconn: Change the expected error for Windows.

On Windows ECONNRESET is WSAECONNRESET.

Also, "unix" connections are done through TCP sockets.
For the 'refuse-connection' test, the error message for Windows
is WSAECONNRESET instead of EPIPE.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>