tipc: set link tolerance correctly in broadcast link

In the patch referred to below we added link tolerance as an additional
criteria for declaring broadcast transmission "stale" and resetting the
affected links.

However, the 'tolerance' field of the broadcast link is never set, and
remains at zero. This renders the whole commit without the intended
improving effect, but luckily also with no negative effect.

In this commit we add the missing initialization.

Fixes: a4dc70d4 ("tipc: extend link reset criteria for stale packet retransmission")
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>