bridge: Don't complain about disappeared cgroups while sampling
bridge: Don't complain about disappeared cgroups while sampling

This is a normal thing to happen.  When listing a directory, one can
not assume that the entry is still there when finally getting around
to opening it.

martinpitt/cockpit,mvollmer/cockpit,garrett/cockpit,garrett/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,mvollmer/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,garrett/cockpit,mvollmer/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,garrett/cockpit,garrett/cockpit,cockpit-project/cockpit,cockpit-project/cockpit