When a recursive unmount fails, don't bother parsing the mount table to check
if what we expected to be a mountpoint is still mounted. `EINVAL` is
returned when you try to unmount something that is not a mountpoint, the
other cases of `EINVAL` would not apply here unless everything is just
wrong. Parsing the mount table over and over is relatively expensive,
especially in the code path that it's in.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Upstream-commit: dd2108766017c13a19bdbfd1a56cd1358580e0bb
Component: engine
a3765ce30c