Track function run session to stop it from the plugin

[lstocchi]

We should track function run sessions as they will spawn an infinite process and we should be able to stop them. It happens that if you close the terminal, func cli doesn't stop them

[lstocchi]

After talking with the serverless team they said they are going to see how to handle it. Maybe by closing the container when the pipe i/o gets closed. Keeping it blocked for now.

[mohitsuman]

Relates to redhat-developer/intellij-knative#93