error: Drop some obviously superfluous error_propagate()

When error_propagate(errp, local_err) is the only reader of
@local_err, we can just as well change its writers to write @errp
directly, and drop the error_propagate() along with @local_err.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20221121085054.683122-2-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>