SSE transport test: fix timing dependency
SSE transport test: fix timing dependency

This relied on a race condition *and* a bug in the creation of the index
wrapper; both bugs were fragile and masked the other. Now we create the
index wrapper with a pubsub registry, and use the blocking lamina
channel->lazy-seq variant for dequeues.

nberger/riemann,rhysr/riemann,tzach/riemann,mbuczko/riemann,pradeepchhetri/riemann,alq666/riemann,zamaterian/riemann,fullcontact/riemann,rekhajoshm/riemann,bfritz/riemann,bmhatfield/riemann,pradeepchhetri/riemann,yeller/riemann,patrox/riemann,jamtur01/riemann,lispmeister/riemann,jeanpralo/riemann,aphyr/riemann,yeller/riemann,joerayme/riemann,algernon/riemann,topecz/riemann,cswaroop/riemann,forter/riemann,rhysr/riemann,zamaterian/riemann,DasAllFolks/riemann,tzach/riemann,patrox/riemann,VideoAmp/riemann-1,forter/riemann,abailly/riemann,rekhajoshm/riemann,algernon/riemann,yeller/riemann,DasAllFolks/riemann,pharaujo/riemann,Anvil/riemann,ClodoCorp/riemann,fullcontact/riemann,robashton/riemann,timbuchwaldt/riemann,AkihiroSuda/riemann,algernon/riemann,topecz/riemann,cswaroop/riemann,LubyRuffy/riemann,robashton/riemann,bg451/riemann,patrox/riemann,jeanpralo/riemann,bmhatfield/riemann,vincentbernat/riemann,riemann/riemann,counsyl/riemann,ClodoCorp/riemann,tzach/riemann,mirwan/riemann,pharaujo/riemann,bwilber/riemann,mbuczko/riemann,irudyak/riemann,aphyr/riemann,rhysr/riemann,AkihiroSuda/riemann,bfritz/riemann,eric/riemann,timbuchwaldt/riemann,lispmeister/riemann,LubyRuffy/riemann,bowlofstew/riemann,micrub/riemann,vixns/riemann,moonranger/riemann,bwilber/riemann,alq666/riemann,mirwan/riemann,fullcontact/riemann,pyr/riemann,vincentbernat/riemann,rekhajoshm/riemann,pyr/riemann,Anvil/riemann,mirwan/riemann,bg451/riemann,micrub/riemann,irudyak/riemann,shokunin/riemann,nberger/riemann,ClodoCorp/riemann,abailly/riemann,joerayme/riemann,counsyl/riemann,bowlofstew/riemann,forter/riemann,moonranger/riemann,micrub/riemann,shokunin/riemann,eric/riemann,VideoAmp/riemann-1,lispmeister/riemann,vixns/riemann,cswaroop/riemann,jamtur01/riemann,riemann/riemann,shokunin/riemann,topecz/riemann