vhost: simplify vhost_dev_init() fail_busyloop label

vhost: simplify vhost_dev_init() fail_busyloop label

Requiring a conditional for every goto is tedious:

  if (busyloop_timeout) {
      goto fail_busyloop;
  } else {
      goto fail;
  }

Move the conditional to into the fail_busyloop label so that it's safe
to jump to this label unconditionally.

This change makes the migrate_add_blocker() error case more consistent.
It jumped to fail_busyloop unconditionally whereas the memslots limits
error case was conditional.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210222114931.272308-1-stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>