test_media_callback_interrupt random failures

The test randomly fails in the CI with the following assert:

test_libvlc_media_callback: ../../../test/libvlc/media_callback.c:236: test_media_callback_interrupt: Assertion `vlc_sem_trywait(&imem->read_blocking) == EAGAIN' failed.

Examples:

• https://code.videolan.org/fuzun/vlc/-/jobs/1759441
• https://code.videolan.org/videolan/vlc/-/jobs/1759393

This seems to be recent. Maybe !5342 (merged) ?