Dedicated HTTPS Agent
Dedicated HTTPS Agent

Avoid modifying the global agent for DocumentDB purposes.
Use a dedicated agent for all of the lib’s requests.

`maxSockets` was set to `Infinity` instead of `10000`, as that’s the purpose of 10000 and Infinity is the default value in latest nodejs versions.

Azure/azure-documentdb-node,rnagpal/azure-documentdb-node