In case ContainerExport() is called for an unmounted container, it leads
to a daemon panic as container.BaseFS, which is dereferenced here, is
nil.
To fix, do not rely on container.BaseFS; use the one returned from
rwlayer.Mount().
Fixes: 7a7357dae1bccc ("LCOW: Implemented support for docker cp + build")
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 81f6307eda44ab3a91de6e29304810a976161d74)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
c9c8799088