Suppress lcb_timer_* deprecation warnings for internal usage

We still need to support some functions. Remove the line noise this
generates.

Change-Id: I10b74ae753fef31d07558ac15415d19399d5d41f
Reviewed-on: http://review.couchbase.org/40984
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>