Merge pull request #2427 from c960657/patch-4

[docker] Ignore mountpoints not accessible by current user

utils/dockerutil.py

@@ -163,7 +163,7 @@ def find_cgroup(self, hierarchy):
 
             candidate = None
             for _, mountpoint, _, opts, _, _ in cgroup_mounts:
-                if hierarchy in opts:
+                if hierarchy in opts and os.path.exists(mountpoint):
                     if mountpoint.startswith("/host/"):
                         return os.path.join(self._docker_root, mountpoint)
                     candidate = mountpoint