coverity: Check return value of fcntl in lxc_popen

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
coverity: Always check mkdir_p's return value

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
coverity: check return value of fcntl in usernsexec

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
coverity: Don't store fgets return value if we don't use it

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
coverity: Drop dead code

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
coverity: Check return value from open

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
bdev: Add aufs support

This is pretty much copy/paste from overlayfs.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>