Do not zoom to route bounding box unconditionally

Currently we change the camera position such that a route fits into the window whenever a route request succeeds. However, right now there are two cases coming to my mind where this is not ideal:

1) We already did an estimation of the bounding box from the given url points and updating the camera position creates a little flickering effect even though the route would be entirely visible anyway

2) We already updated the map bounds for the first /route request, but when the second /route request (that includes alternative routes) succeeds we update the map bounds again. This is especially annoying when the alternative routes take some time and the user already started zooming/panning the map. E.g. load this URL, pan the map and you will see it jumps back at some point: http://localhost:3000/?point=48.988641%2C7.180233&point=50.856244%2C12.297411&profile=foot&layer=OpenStreetMap

Nothing major, but keeping this as a reminder here.

Related to #306.