Messages screen can be pushed twice in the navigation stack in extreme scenario

[atsakiridis]

Scenario:

• Open Messages screen
• Receive call while on Messages screen
• Receive a message while on Call screen

After the call is terminated we are left in a Message screen which is separate than the first message screen.

We need to only allow one message screen at all times

[atsakiridis]

Deferring to GA since the effort is minimum and not related to SDK