vsock/test: fix vsock_ioctl_int() check for unsupported ioctl

`vsock_do_ioctl` returns -ENOIOCTLCMD if an ioctl support is not
implemented, like for SIOCINQ before commit f7c72265 ("vsock: Add
support for SIOCINQ ioctl"). In net/socket.c, -ENOIOCTLCMD is re-mapped
to -ENOTTY for the user space. So, our test suite, without that commit
applied, is failing in this way:

    34 - SOCK_STREAM ioctl(SIOCINQ) functionality...ioctl(21531): Inappropriate ioctl for device

Return false in vsock_ioctl_int() to skip the test in this case as well,
instead of failing.

Fixes: 53548d6b ("test/vsock: Add retry mechanism to ioctl wrapper")
Cc: niuxuewei.nxw@antgroup.com
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>
Link: https://patch.msgid.link/20250715093233.94108-1-sgarzare@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>