tests/check/elements/: consistent pad (de)activation

tests/check/elements/: consistent pad (de)activation

Original commit message from CVS:
* tests/check/elements/audiopanorama.c: (cleanup_panorama):
* tests/check/elements/avimux.c: (setup_avimux), (cleanup_avimux):
* tests/check/elements/cmmldec.c: (setup_cmmldec),
(teardown_cmmldec):
* tests/check/elements/cmmlenc.c: (setup_cmmlenc),
(teardown_cmmlenc):
* tests/check/elements/level.c: (setup_level), (cleanup_level):
consistent pad (de)activation