tests: insertbin: update tests to 1.x scenario

The thread that calls the success/failure callback can be the
same that is adding/removing the element as the IDLE probe can
happen instantly if the pad is not 'busy'.

This required moving some checks for the callback counter around
as well as removing some pad pushes from the main test thread as
they were made useless after the IDLE pad probe was fixed in core
by commit 0324358ebc8122a41ab499a3ef7973b61c3e621b
check: Update uvch264demux for behaviour change

Since 006e7a3428bd097fc6e6c648332bff583dd434f9 we no longer error out on
incomplete aux segment.