virtio-devices, vmm: Update seccomp list

The seccompiler v0.4.0 started to use `seccomp` syscall instead of the
`prctl` syscall. Also, threads for virtio-deivces should not need any of
these syscalls anyway.

Signed-off-by: Bo Chen <chen.bo@intel.com>

vmm/src/seccomp_filters.rs

@@ -607,6 +607,7 @@ fn vmm_thread_rules(
         (libc::SYS_rt_sigreturn, vec![]),
         (libc::SYS_sched_getaffinity, vec![]),
         (libc::SYS_sched_setaffinity, vec![]),
+        (libc::SYS_seccomp, vec![]),
         (libc::SYS_sendmsg, vec![]),
         (libc::SYS_sendto, vec![]),
         (libc::SYS_set_robust_list, vec![]),