aa-unconfined: Fix race when reading proc/*/attr/current
aa-unconfined can fault if it looses the race between checkking if proc/*/attr/{apparmor/,}current exists, and actually opening the file. Catch open/file errors and ignore them like the file doesn't exist.
Fixes: #355 (closed) Signed-off-by: John Johansen john.johansen@canonical.com