Alexa needs 2 roles,

one for playing music, and one for speech

The current used ones are respectively 'emergency' and 'navigation"

It should use multimedia for music, and a dedicated role for speech.

Moreover, it does not release the role, which makes the master volume

always attach to it.

So the actions are:

1) in 4a

• Add a dedicated 'speech' role (and matching stream in the hal)

2) in Alexa

• use the right roles in the configuration file
• always release the role when it is not used anymore