Be consistent wrt vsl_ts locking
Be consistent wrt vsl_ts locking

Fix an issue where the new timestamp was set without locking.

Spotted by: Coverity

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