varnish/vhost.vcl: fix logic inversion in redirection
varnish/vhost.vcl: fix logic inversion in redirection

SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-site