It is sufficient to have capabilities in the owning user namespace of
the mount namespace to list all mounts regardless of whether they are
reachable or not.

Link: https://lore.kernel.org/r/8adc0d3f4f7495faacc6a7c63095961f7f1637c7.1719243756.git.josef@toxicpanda.comSigned-off-by: Christian Brauner <brauner@kernel.org>