This is sort of embarrasing:  I forgot to lock the busyobj when changing the storage list.
This is sort of embarrasing:  I forgot to lock the busyobj when
changing the storage list.

Fixes: #1839

gquintard/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache,franciscovg/Varnish-Cache,feld/Varnish-Cache,varnish/Varnish-Cache,varnish/Varnish-Cache,franciscovg/Varnish-Cache,feld/Varnish-Cache,franciscovg/Varnish-Cache,varnish/Varnish-Cache,feld/Varnish-Cache,varnish/Varnish-Cache,feld/Varnish-Cache,franciscovg/Varnish-Cache,varnish/Varnish-Cache,gquintard/Varnish-Cache,franciscovg/Varnish-Cache