Move login token code into the "RECONNECT TOKENS" section.
Closing a session should be idempotent.
Space out code for readability.
Run nodejs stream client callbacks in a fiber.

Poll instead of using Deps.autorun in server test.

When polling the client connection, tests don't have a chance to
disconnect before the stream client automatically reconnects, so add
an option to disable retries for testing.

Callers of `Meteor.bindEnvironment` often have the `onException`
argument print the exception stack trace.  To allow for less code
duplication, let the argument be a string providing the context
(e.g. "connection closed callback"), and then on an exception print
the context and the exception stack trace.