Work around the delay to add a sequence job item, consider invalid exposure and count.

When the test code adds a job item in the Capture UI, it takes a few signals to actually register the fields into a new item.

This MR waits for the queue table to register one more item before continuing to add items.

The impact on UI is minor, as it would be very difficult for someone to click the 'add' button and modify one of the fields before the new item is added. Therefore, that edge case is only worked around and not verified.