nfsv3: fix creation of symbolic link

Do not check inode existence as backed VFS
implementation (Chimera) already does it.

Acked-by: Gerd Behrmann
Target: master, 0.6, 0.5
Require-book: no
Require-notes: no
(cherry picked from commit 3252e045a6fbbd0021a615b658440d71ee06cabe)
Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>