This commit sets the client capability value to not pass
unknown users data in the webapp and also does some changes
to avoid errors while loading the web-app home page.
This commit only does some basic webapp changes to not show
inaccessible users in sidebar and we would need need more
changes to make the web-app work as expected which will be
done in further commits.
We have already fixed the actual bugs that were resulting in client
receiving presence data for unknown user, so we can remove the
blueslip logging and just skip the unknown users.
Anders Kaseorg
Sahil Batra
Lalit