Currently the Refresh methods will always queue a refresh as a
background operation. This is because the methods could be triggered
from a coroutine running the engine updates. All the other callers
though are running in the main thread and this use of queued updates
causes perceptible delays in the view changing.

We can simplify this by handling refreshes synchronously, but changing
the only background goroutine caller to use a queue update.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>