Disable other suggestions in discussion when applying

The following discussion from gitlab-ce!28160 should be addressed:

• @pslaughter started a discussion:

  note: It's kind of problematic that we handle isApplying as internal state to this component:

  • Complexity for passing callback in event emitter.
  • Can't disable other suggestion's when applying one.

  I'm going to create a follow up issue to address this.