Newly created circle has no "wall" timeline room

When we create a new circle, we are creating its rooms in the wrong order. Currently we create a new empty circle space, and then we use it to create its "wall" timeline room.

The problem is that when the second call to /createRoom fails, then we have a broken circle with no wall room where we can post or invite followers.

Instead, we should first create the timeline room, and then only if that succeeds, we should create the circle space to contain it.