Do not run unlinked files test on passthrough_hp with old kernels

Do not run unlinked files test on passthrough_hp with old kernels

test_syscalls unlinked testfiles check fails on passthourhg_hp without
the kernel commit "fuse: fix illegal access to inode with reused nodeid"
queued for kernel 5.14 [1].

Make this check opt-in and do not run it with kernel version before 5.14.

[1] https://lore.kernel.org/linux-fsdevel/CAJfpegtGKjeK8E5QsHKF0=re1J9wVHuGRVgg9NDJ_OOwQdCUNg@mail.gmail.com/

Signed-off-by: Amir Goldstein <amir73il@gmail.com>