Multiple Steam NetConnections to a single session are recorded incorrectly during cleanup

When introduced with two Steam NetDrivers/NetConnections to the same user, instead of closing out the communications on a per channel basis, the entire session is removed from the connection list. This incorrectly handles the data that we do have about a connection and can cause issues regarding data being sent.

It's also potentially what causes communications to timeout incorrectly.

1. Create a project with two beacons that use Steam NetDrivers
2. Host a session with the two beacons
3. Have a client on Steam that connections to the host
4. Have the client or host close one of the beacon connections
5. Observe in the logs that several timeouts occur suddenly on all connections to the client