client/fuse: Fix directory DACs overriding for root

client/fuse: Fix directory DACs overriding for root

DACs are overridable for directories. For files,
Read/write DACs are always overridable but executable
DACs are overridable when there is at least one exec bit
set.

The files and directory DACS overriding were handled the
same way for root which is incorrect. This patch fixes
DACs overriding as described above for the root.

Fixes: https://tracker.ceph.com/issues/55313
Signed-off-by: Kotresh HR <khiremat@redhat.com>
(cherry picked from commit 2e1f43c99b1818c2ffde64f5b01083c1907a9f87)