netdevsim/nexthop-sh is flaky on debug

Hi Ido!

Hope you don't mind two reports in a row..

Looks like netdevsim/nexthop.sh has gotten a lot flakier on debug kernels since around the time of commit 25bf7d7f458c ("Merge branch 'neighbour-convert-rtm_getneigh-to-rcu-and-make-pneigh-rtnl-free'") It has always been a little flaky (4 flakes in May, 7 flakes in June) but after the commit in question we got 8 flakes in 2 weeks.