We had two problems with /dev/shm, first, you mount the
container read/only then /dev/shm was mounted read/only.
This is a bug a tmpfs directory should be read/write within
a read-only container.
The second problem is we were ignoring users mounted /dev/shm
from the host.
If user specified
podman run -d -v /dev/shm:/dev/shm ...
We were dropping this mount and still using the internal mount.
Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>