fuse: remove an unnecessary if statement

FUSE remote locking code paths never add any locking state to
inode->i_flctx, so the locks_remove_posix() function called on
file close will return without calling fuse_setlk().

Therefore, as the if statement to be removed in this commit will
always be false, remove it for clearness.

Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>