[System] Fixed HttpWebRequest test that sometimes failed

The TestTimeoutPropertyWithServerThatDoesntExist test sometimes failed with a 'ConnectFailure' instead
of a 'Timeout', presumably because connecting to the non-existing IP failed earlier than the timeout was reached.
Using a public, existing IP (but still with a port where no service listens) made this test reliable for me.

Additionally, the assert which checks for the correct exception switched the 'expected' and 'actual' parameter, which resulted in the wrong output.

I'm actually not sure if this test is even testing the right thing (i.e. it sounds plausible that the connection fails before the timeout if the IP doesn't exist).
@knocte: you added this test, do you remember some context about this? The linked bug doesn't seem to go into much detail about why this would be the correct behavior.