Make vcl_set_state accept a ctx instead of a vcl
Make vcl_set_state accept a ctx instead of a vcl

This paves the way towards failing VCL_EVENT_WARM events in VMODs. If
setting the temperature fails, we may need to carry a message back to
the CLI and other bits of context.

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