We should include details of TCP timeout on the azure page

As covered in https://docs.microsoft.com/en-us/azure/load-balancer/load-balancer-tcp-idle-timeout, the default tcp keep alive for azure load balancers is 4 minutes.

This has a knock-on effect for Couchbase Server users as generally the azure templates configure each node to use the public IP address, so the tcp timeout for these is also 4 minutes.

We need to add a section onto the networking section of this page to recommend that users configure their TCP keepalives on all connecting applications to be significantly lower than this 4 minute timeout, to ensure connections are not unexpectedly closed.
For example, the default keepalive for Windows (and in the .NET SDK) is 2 hours, which is much higher than the 4 minute timeout, so connections may get closed early and cause significant problems.