installer: Fix recently introduced format / argument breakage.

It's __printflike(1, 3) but I treated it like __printflike(1, 2) in
9462167aa18776bf92c161a3c65740189ffe8912.

Reported-by: Joe White <hybris246@gmail.com>
serialize: Rework adaptive enter

- Don't increase wait counter before the spinning phrase; this avoids
  unnecessary wakeup() calls on other CPU
- Rework the spinning phrase according to our spinlock contest processing

Tested on 8 HT (i7-3770) box, using kq_accept_server/kq_connect_client:
- 4/4 TX/RX rings device (BCM5719, using MSI-X), slight improvement.
- 8/8 TX/RX rings device (Intel 82580, using MSI-X), slight improvement.
- 1/2 TX/RX rings device (Intel 82599, using MSI), slight improvement.