If the OC doesn't have a boc, don't lock unnecessarily lock the OH
If the OC doesn't have a boc, don't lock unnecessarily lock the OH

The objcore won't gain a boc in a way that would call for locking the
OH when checking if it wasn't there in the first place. So if the
oc->boc is NULL, return early. This saves a mutex lock/unlock in the
common case.

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