message: Ensure we only start one instance of OmniSharp server
diff: @@ -250,6 +250,10 @@ export class OmniSharpServer {
  // --- start, stop, and connect
  private async _start(launchTarget: LaunchTarget, options: Options): Promise<void> {
  + if (this._state != ServerState.Stopped) {
  + this.eventStream.post(new ObservableEvents.OmnisharpServerOnServerError("Attempt to start OmniSharp server failed because another server instance is running."));
  + return;
  + }
  if (launchTarget.kind === LaunchTargetKind.LiveShare) {
  this.eventStream.post(new ObservableEvents.OmnisharpServerMessage("During Live Share sessions language services are provided by the Live Share server."));
  @@ -498,6 +502,11 @@ export class OmniSharpServer {
  }
  public async restart(launchTarget: LaunchTarget = this._launchTarget): Promise<void> {
  + if (this._state == ServerState.Starting) {
  + this.eventStream.post(new ObservableEvents.OmnisharpServerOnServerError("Attempt to restart OmniSharp server failed because another server instance is starting."));
  + return;
  + }
  +
  if (launchTarget) {
  await this.stop();
  this.eventStream.post(new ObservableEvents.OmnisharpRestart());
  