Use node-XMLHttpRequest instead of XHR2 for synchronous calls?

[kood1]

Since XHR2 doesn't support sync calls, we should consider the following for msl-client-node:

1. Use a different library - https://github.com/driverdan/node-XMLHttpRequest
2. Build polling ourselves inside node client

[kood1]

We should test large responses with node-XMLHttpRequest since it failed before.