The tests for Downward API volume were apparently created before the
default sync-frequency was set to 1 minute. As the current
implementation of Pod gives us no guarantee that the changes will be
seen in Downward API before `sync-frequency` we need the tests to
reflect this.
Fixes: #29633
This implements the proposal in:
docs/proposals/secret-configmap-downwarapi-file-mode.md
Fixes: #28317.
The mounttest image is updated so it returns the permissions of the linked file
and not the symlink itself.