vfs cache: Fallback to namei to resolve symlinks with leading / in target for non-native ABI

This is a temporary solution to fix PR before release.
During 15.0 it's necessary to refactor symlinks handling
between vfs & namecache.

Approved by: re (gjb)
PR: 273414
Reported by: Vincent Milum Jr, Dan Kotowski, glebius
Tested by: Dan Kotowski, glebius
Reviewed by:
Differential Revision: https://reviews.freebsd.org/D41806
MFC after: 3 days

(cherry picked from commit bb8ecf259f96510b9c2146d846403393543061b7)
(cherry picked from commit b84a836ef02de42e262ce44d46c859be288df4b0)