zebra: use a small retry timeout for the rib workqueue

zebra: use a small retry timeout for the rib workqueue

In the zebra rib processing workqueue, set a small timeout
so that we will wait a short time if the queue into the
async dataplane is full. This helps avoid a situation where
the zebra main pthread constantly retries rib work without
giving the dataplane pthread a chance to make progress.

Signed-off-by: Mark Stapp <mjs@voltanet.io>