mount: fix regression detached mount tree regression

When we disabled mount propagation into detached trees again this
accidently broke mounting detached mount trees onto other detached mount
trees. The selftests fail and Alison reported it yesterday as well.
Fix the regression.

Fixes: 3b5260d12b1f ("Don't propagate mounts into detached trees")
Signed-off-by: Christian Brauner <brauner@kernel.org>
1 file changed