When the source of the copy operation is the root directory, we should
neither append it to the destination path on FTS_D nor trim it back off
on FTS_DP.
Approved by: re (cperciva)
PR: 291132
MFC after: 3 days
Fixes: 82fc0d09e8 ("cp: Partly restore symlink folllowing.")
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D53863
(cherry picked from commit fe836c5012)
(cherry picked from commit c4843e5805)
Dag-Erling Smørgrav
54808d5041