fusefs: fix conditional from r351061

The entirety of r351061 was a copy/paste error. I'm sorry I've been
comitting so hastily.

Reported by: rpokala
Reviewed by: rpokala
MFC after: 2 weeks
MFC-With: 351061
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21265