This's an optimization to get rid of redundant `/dev/shm" mounts for pause container. In `oci.defaultMounts`, there is a default `/dev/shm` mount which is redundant for pause container. Fixes: #6911 Signed-off-by: Jiang Liu <gerry@linux.alibaba.com> Signed-off-by: Lei Wang <wllenyj@linux.alibaba.com>