selftests/vsock: increase timeout to 1200

selftests/vsock: increase timeout to 1200

Increase the timeout from 300s to 1200s. On a modern bare metal server
my last run showed the new set of tests taking ~400s. Multiply by an
(arbitrary) factor of three to account for slower/nested runners.

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Link: https://patch.msgid.link/20260121-vsock-vmtest-v16-4-2859a7512097@meta.com
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>