Do not broadcast initialization data to all clients.

Instead, send the data as a response to the initialization request
message. This simplifies the code and makes it more predictable, as we
do not spam all clients with initialization broadcasts anymore.

Note that the pending initialization "feature" is removed, but I don't
see a need for it anymore. If you want to delay client initialization,
do it on the client side.

Change-Id: I1ab71fd6c9e809ccb6085f1a3fbac3eb9b2e910b
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>