Major Description
In the kernel sub-project's org.apache.toree.kernel.api.Kernel.scala, when we do the spark context delayed initialization, there is hardcoded wait of 100 ms. This usually works ok, but in slow machines or busy nodes it's not enough and cause confusion to users as it's going to try to initialize the context and display the message on the notebook ui twice.
We should enable users to configure the timeout via an environment variable.
