Fixes #14067 - Host#edit integration tests should wait for tasks

When you click on Host#edit Submit button, a few orchestration tasks
will be created. After that, the show page will call (via AJAX) a few
URLS to fetch 'overview', 'resources', 'nics', etc... to fill up the
table on the left side. These are all irrelevant to tests that only
concern the form, and pose a problem as we don't explicitly wait for
them.

Problem:
The server we test on is not multithreaded, these tasks will run
sequentially. Therefore, the default Capybara waiting time, or
Capybara.default_max_time might not be enough to wait for all requests.

Solution:
We can wait until the #host-progress div has disappeared and wait for
the Host#show ajax calls using wait_for_ajax