Phone call transfers playback to desktop; shouldn't

[alexkorn]

Steps to reproduce:
1. Listen to Spotify on iPhone; have Spotify open (but not being used) on a Mac on the same WiFi network.

2. Receive a phone call.

3. Spotify stops music on the iPhone, but automatically starts playing it on the Mac.

I just want music to stop/pause when I receive a phone call.

The potential outcomes to this are:

1. When I receive a phone call, suddenly music starts blasting out of my laptop. Not good.

2. I've hand-picked an hour or so of music to play and have my Mac muted, so I don't even notice that the music playback has "transferred" to the Mac. So after an hour-long phone call, I realize that the whole "Up next" playlist I'd created has played through and is now gone. Also not good.

(In general, the integration across devices is awesome, but this aspect of it is bad.)