Slow spectating join will irreversibly leave a matchmaking game

[valve76]

Repro

1. Enter the matchmaking queue
2. Request to start spectating a game - requires the spectating join to take longer than the matchmaking queue
3. Have the matchmaking queue complete, and load into the game
4. Have the spectating join complete

Actual

The player is removed from the matchmaking game and switches to spectating. No option to rejoin the matchmaking game after the leaving the spectator game is present - i.e. it is impossible to rejoin the matchmaking game.

Expected

Any attempt to spectate a game should be automatically cancelled when a matchmaking game is found, or it should be impossible for a player to be switched away from a matchmaking game for "automatic" reasons.