c/r: enable tracefs
c/r: enable tracefs

tracefs is a new filesystem that can be mounted by users. Only the options
and fs name need to be passed to restore the state, so we can use criu's
auto fs feature.

Signed-off-by: Tycho Andersen <10c18fcb898ee6b17d6575d444b125d10b3f4d6a@canonical.com>
Acked-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

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