Ensure sessionEnded request is correctly mapped in Virtual Google Assistant

[jperata]

Is your feature request related to a problem? Please describe.
Ensure sessionEnded request is correctly mapped in Virtual Google Assistant, by checking the "sessionEnded": true property. Trying this out with Guess The Price for Google repository shows the sessionEnded flag on every single response, so it's probably an issue with the google assistant library itself or an unknown behavior.

Describe the solution you'd like
The sessionEnded flag should correctly indicate if it's the end of the session for a google assistant action.

Additional context
Guess The Price for Google can be used to test this. It should indicate sessionEnded at the end of the skill but not before that.