https://github.com/mongodb/node-mongodb-native/pull/3621 deprecated tcp keep alive options.  These options also have defaults in the URI parser.

Our uri parsing logic works as follows:

• once we've accumulated all provided options, we then start assigning default values
• to do this, we iterate over all options that have defaults provided and set them on the options object
• When we set an option, we check if the option is deprecated.  if it is, we emit a deprecation warning

Consequently, even when keepAlive and keepAliveInitialDelay are unset, we emit warnings for these options.