src/vs/platform/remote/common/tunnel.ts/AbstractTunnelService/removeEmptyTunnelFromMap
class AbstractTunnelService:	private async removeEmptyTunnelFromMap(remoteHost: string, remotePort: number) {
		const hostMap = this._tunnels.get(remoteHost);
		if (hostMap) {
			const tunnel = hostMap.get(remotePort);
			const tunnelResult = await tunnel;
			if (!tunnelResult) {
				hostMap.delete(remotePort);
			}
			if (hostMap.size === 0) {
				this._tunnels.delete(remoteHost);
			}
		}
	}