iotests: massive use _qcow2_dump_header

iotests: massive use _qcow2_dump_header

We are going to add filtering in _qcow2_dump_header and want all tests
use it.

The patch is generated by commands:
  cd tests/qemu-iotests
  sed -ie 's/$PYTHON qcow2.py "$TEST_IMG" dump-header\($\| \)/_qcow2_dump_header\1/' ??? tests/*

(the difficulty is to avoid converting dump-header-exts)

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20211223160144.1097696-15-vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>