casper: Clean up default stream tests a bit more.
casper: Clean up default stream tests a bit more.

This users casper.then in a more reasonable way, and also moves the
stream_name definition to the section where it's used.

ryanbackman/zulip,shubhamdhama/zulip,christi3k/zulip,blaze225/zulip,synicalsyntax/zulip,kou/zulip,aakash-cr7/zulip,andersk/zulip,dattatreya303/zulip,susansls/zulip,sonali0901/zulip,amanharitsh123/zulip,susansls/zulip,j831/zulip,shubhamdhama/zulip,shubhamdhama/zulip,christi3k/zulip,showell/zulip,mahim97/zulip,aakash-cr7/zulip,vaidap/zulip,vaidap/zulip,samatdav/zulip,jphilipsen05/zulip,brainwane/zulip,zulip/zulip,dhcrzf/zulip,jphilipsen05/zulip,vabs22/zulip,jainayush975/zulip,aakash-cr7/zulip,vabs22/zulip,susansls/zulip,jrowan/zulip,verma-varsha/zulip,synicalsyntax/zulip,andersk/zulip,jphilipsen05/zulip,jrowan/zulip,SmartPeople/zulip,brockwhittaker/zulip,sonali0901/zulip,PhilSk/zulip,jackrzhang/zulip,ryanbackman/zulip,ryanbackman/zulip,christi3k/zulip,j831/zulip,blaze225/zulip,souravbadami/zulip,hackerkid/zulip,susansls/zulip,vabs22/zulip,dhcrzf/zulip,rishig/zulip,tommyip/zulip,JPJPJPOPOP/zulip,verma-varsha/zulip,j831/zulip,shubhamdhama/zulip,synicalsyntax/zulip,Galexrt/zulip,rishig/zulip,kou/zulip,andersk/zulip,christi3k/zulip,sonali0901/zulip,hackerkid/zulip,SmartPeople/zulip,synicalsyntax/zulip,jainayush975/zulip,blaze225/zulip,eeshangarg/zulip,hackerkid/zulip,j831/zulip,SmartPeople/zulip,zulip/zulip,punchagan/zulip,rht/zulip,synicalsyntax/zulip,dawran6/zulip,showell/zulip,PhilSk/zulip,rht/zulip,susansls/zulip,hackerkid/zulip,souravbadami/zulip,brockwhittaker/zulip,brainwane/zulip,dhcrzf/zulip,j831/zulip,Galexrt/zulip,mahim97/zulip,synicalsyntax/zulip,hackerkid/zulip,amanharitsh123/zulip,andersk/zulip,jackrzhang/zulip,dhcrzf/zulip,amanharitsh123/zulip,JPJPJPOPOP/zulip,hackerkid/zulip,tommyip/zulip,SmartPeople/zulip,rishig/zulip,amanharitsh123/zulip,timabbott/zulip,timabbott/zulip,punchagan/zulip,brockwhittaker/zulip,shubhamdhama/zulip,brainwane/zulip,punchagan/zulip,jrowan/zulip,dawran6/zulip,jphilipsen05/zulip,tommyip/zulip,vaidap/zulip,sonali0901/zulip,aakash-cr7/zulip,showell/zulip,Galexrt/zulip,samatdav/zulip,synicalsyntax/zulip,rht/zulip,tommyip/zulip,jackrzhang/zulip,Galexrt/zulip,kou/zulip,SmartPeople/zulip,eeshangarg/zulip,timabbott/zulip,blaze225/zulip,jackrzhang/zulip,punchagan/zulip,Galexrt/zulip,andersk/zulip,dhcrzf/zulip,andersk/zulip,mahim97/zulip,punchagan/zulip,dattatreya303/zulip,j831/zulip,eeshangarg/zulip,rht/zulip,andersk/zulip,amanharitsh123/zulip,eeshangarg/zulip,samatdav/zulip,tommyip/zulip,eeshangarg/zulip,sonali0901/zulip,ryanbackman/zulip,rishig/zulip,vaidap/zulip,SmartPeople/zulip,brainwane/zulip,jphilipsen05/zulip,kou/zulip,hackerkid/zulip,kou/zulip,dawran6/zulip,aakash-cr7/zulip,dattatreya303/zulip,dhcrzf/zulip,timabbott/zulip,jrowan/zulip,blaze225/zulip,brockwhittaker/zulip,dattatreya303/zulip,samatdav/zulip,vabs22/zulip,Galexrt/zulip,ryanbackman/zulip,dhcrzf/zulip,dattatreya303/zulip,PhilSk/zulip,JPJPJPOPOP/zulip,rishig/zulip,verma-varsha/zulip,brainwane/zulip,vabs22/zulip,tommyip/zulip,kou/zulip,ryanbackman/zulip,jainayush975/zulip,rishig/zulip,showell/zulip,punchagan/zulip,mahim97/zulip,dawran6/zulip,dattatreya303/zulip,PhilSk/zulip,souravbadami/zulip,kou/zulip,zulip/zulip,jphilipsen05/zulip,brainwane/zulip,jainayush975/zulip,brockwhittaker/zulip,vaidap/zulip,tommyip/zulip,souravbadami/zulip,rht/zulip,dawran6/zulip,samatdav/zulip,christi3k/zulip,verma-varsha/zulip,verma-varsha/zulip,christi3k/zulip,eeshangarg/zulip,souravbadami/zulip,jackrzhang/zulip,jainayush975/zulip,zulip/zulip,jackrzhang/zulip,verma-varsha/zulip,amanharitsh123/zulip,sonali0901/zulip,jackrzhang/zulip,susansls/zulip,shubhamdhama/zulip,zulip/zulip,showell/zulip,aakash-cr7/zulip,PhilSk/zulip,JPJPJPOPOP/zulip,jrowan/zulip,mahim97/zulip,jrowan/zulip,dawran6/zulip,PhilSk/zulip,rishig/zulip,showell/zulip,zulip/zulip,blaze225/zulip,rht/zulip,JPJPJPOPOP/zulip,timabbott/zulip,souravbadami/zulip,showell/zulip,Galexrt/zulip,timabbott/zulip,vaidap/zulip,punchagan/zulip,rht/zulip,zulip/zulip,jainayush975/zulip,shubhamdhama/zulip,eeshangarg/zulip,JPJPJPOPOP/zulip,timabbott/zulip,mahim97/zulip,brockwhittaker/zulip,samatdav/zulip,vabs22/zulip,brainwane/zulip