Fix CORS error when using library with Browserify

[debugthings]

Customers are starting to use the AppInsights node.js SDK to develop browser applications thanks to browserify. This creates a shim for any http.request and https.request call so it redirects to XMLHttpRequest. Unforutnately, this shim defaults to setting withCredentials.

This specific setting does not like the wildcard value for the Access-Control-Allow-Origin header.

Browserify code that causes the problem, that has not been fixed for about 2.5 years now.

Recommended that we add an explicit withCredentials = false in the sender library to avoid these exceptions.

XMLHttpRequest cannot load https://dc.services.visualstudio.com/v2/track. 
Response to preflight request doesn't pass access control check: The value of the 
'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the 
request's credentials mode is 'include'. Origin 'https://YOURSERVER.ADDRESS.COM/' is therefore 
not allowed access. The credentials mode of requests initiated by the XMLHttpRequest is 
controlled by the withCredentials attribute.

[msftclas]

This seems like a small (but important) contribution, so no Contribution License Agreement is required at this point. We will now review your pull request.
Thanks,
Microsoft Pull Request Bot