fix LostHeader message in http_PrintfHeader
fix LostHeader message in http_PrintfHeader

When out of workspace, we dumped the piece of memory at the ws free pointer,
which does not necessarily contain anything sensible in this situation.

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