Common Play framework interacts weird with active timer

[osheroff]

Describe the bug
With a running timer, starting to play a song with the CPS asks "do you want to stop the running timer"? This line:

mycroft-core/mycroft/skills/common_play_skill.py

Line 163 in 1b67bf3

self.bus.emit(message.forward("mycroft.stop"))

emits a "mycroft.stop" event, which is interpreted by the timer skill as intending to stop the timer.

To Reproduce
Steps to reproduce the behavior:

1. "Start a timer for 5 minutes"
2. "Play songs by Tom Waits on Spotify"