Fix r01684.vtc logexpect handling
Fix r01684.vtc logexpect handling

The script lacked a logexpect -wait at the end telling it to actually
wait for the required log content.

Added a new rule to match first on an actual retry backend transaction
and match the header set/unset/set tests on that vxid.

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