Bug 32642: (QA follow-up) Activate spinner early

Bug 32642: (QA follow-up) Activate spinner early

See comment on former patch too. We need to activate the spinner
early and we can simplify the code to remove it.

Note: unfortunately this is kind of a workaround, since using
load would be nicer but currently hard to implement since the cover
image code is scattered/widespread.

This code still checks the complete attribute, we could argue that
it should just remove the spinner. Note too that the spinner belongs
to a div where multiple img may be part of. If we do not remove the
spinner now, something went wrong at load time, but if you can
actually see the spinner is another thing.

Test plan:
See former patch.
Check few cover images on detail page, enable various providers.
Bonus: I tested with a sleep statement in opac-image.pl.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>