It has been pointed out that we're ignoring EINVAL from umount(2)
everywhere, so let's move it to a lower-level function. Also, its
implementation should be the same for any UNIX incarnation, so
let's consolidate it.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 90be078fe59a8cfeff2bcc5dc2f34a00309837b6)
Upstream-commit: 47c51447e1b6dacf92b40574f6f929958ca9d621
Component: engine