Fix avatar message display regression from 1.5 release.
Fix avatar message display regression from 1.5 release.

In f75af94984d5f21b22336f4d3f643706425d4695 I added some
lines of code that made it so that live updates for avatar
urls would affect messages currently in the browser.

This change worked well when the live update actually happened,
but then the next time the user would reload, the avatar in
the message pane would regress back to showing the avatar urls
from the server (which could have caching issues of their own).

This fix removes a couple lines of code that had the intended
effect of making all of your messages from any given sender
show the same url (good) but which generally grabbed
the url from an old message (bad).

After this fix, we go back to having old messages possibly
showing the old avatar urls, but new messages will display the
new avatar.

(There are lots of moving parts in the avatar system, because
not only do browsers cache image urls, but our server caches
messages and recipient info, so there have been "fixes" to
avatars since this change that are valid fixes in their own
right but not directly relevant to this commit.)

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