Specifically, none of the graphdrivers are supposed to return a
not-exist type of error on remove (or at least that's how they are
currently handled).
Found that AUFS still had one case where a not-exist error could escape,
when checking if the directory is mounted we call a `Statfs` on the
path.
This fixes AUFS to not return an error in this case, but also
double-checks at the daemon level on layer remove that the error is not
a `not-exist` type of error.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
(cherry picked from commit d42dbdd3d48d0134f8bba7ead92a7067791dffab)
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
b6df63d5f6