inotify: Work around the vput() bug directly

For 15.0, apply a minimal fix which at least ensures that inotify can't
trigger the latent race described in commit 99cb3dca4773 ("vnode: Rework
vput() to avoid holding the vnode lock after decrementing").

Reviewed by: olce, kib
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D53774

(cherry picked from commit ebc17879f0885ca87644980f6275b9759b311eb3)