Bring default for IsBypassed inline with actual implementation

[Mpdreamz]

This brings our IWebProxy implementation inline with the one shipped in netfx/standard/.

/// <summary>Gets or sets a value that indicates whether to bypass the proxy server for local addresses.</summary>
/// <returns>
/// <see langword="true" /> to bypass the proxy server for local addresses; otherwise, <see langword="false" />. The default value is <see langword="false" />.</returns>
public bool BypassProxyOnLocal { get; set; }

[stevejgordon]

LGTM

[flobernd]

LGTM!