Fix: search path is not added when one of its parent is not accessible

When /foo/bar/baz is added to the search paths and if getattr (stat())
is not allowed on one of its parent paths, i.e., /foo and /foo/baz, the
path was thought as non-existent and wasn't added to the search paths of
the namespace.

Fixing the bug by adding the path if the path (though not the parents)
does exist.

Bug: 119656753
Test: m apex.test; m; device boots.
Change-Id: I21bca1fee9aa20688ce9b72192d3173821ad91a3