setup-apt-repo: Clean up setup code for apt repo.
setup-apt-repo: Clean up setup code for apt repo.

This fixes adding the Ubuntu repositories for Debian, as well as makes
sure that we install the debian-archive-keyring package on Debian,
which is only priority important (and thus might be missing).

kou/zulip,rht/zulip,punchagan/zulip,eeshangarg/zulip,andersk/zulip,synicalsyntax/zulip,punchagan/zulip,timabbott/zulip,eeshangarg/zulip,tommyip/zulip,rht/zulip,tommyip/zulip,hackerkid/zulip,timabbott/zulip,synicalsyntax/zulip,zulip/zulip,synicalsyntax/zulip,kou/zulip,andersk/zulip,kou/zulip,dhcrzf/zulip,hackerkid/zulip,brainwane/zulip,rishig/zulip,kou/zulip,jackrzhang/zulip,punchagan/zulip,jackrzhang/zulip,showell/zulip,timabbott/zulip,shubhamdhama/zulip,shubhamdhama/zulip,brainwane/zulip,shubhamdhama/zulip,zulip/zulip,eeshangarg/zulip,hackerkid/zulip,zulip/zulip,rishig/zulip,shubhamdhama/zulip,kou/zulip,eeshangarg/zulip,showell/zulip,showell/zulip,punchagan/zulip,jackrzhang/zulip,brainwane/zulip,jackrzhang/zulip,tommyip/zulip,rishig/zulip,punchagan/zulip,timabbott/zulip,punchagan/zulip,dhcrzf/zulip,kou/zulip,hackerkid/zulip,rishig/zulip,shubhamdhama/zulip,dhcrzf/zulip,brainwane/zulip,jackrzhang/zulip,rht/zulip,showell/zulip,rht/zulip,andersk/zulip,jackrzhang/zulip,tommyip/zulip,synicalsyntax/zulip,showell/zulip,rishig/zulip,brainwane/zulip,timabbott/zulip,timabbott/zulip,synicalsyntax/zulip,eeshangarg/zulip,rishig/zulip,jackrzhang/zulip,tommyip/zulip,dhcrzf/zulip,brainwane/zulip,hackerkid/zulip,rht/zulip,synicalsyntax/zulip,brainwane/zulip,timabbott/zulip,showell/zulip,shubhamdhama/zulip,zulip/zulip,zulip/zulip,andersk/zulip,zulip/zulip,hackerkid/zulip,dhcrzf/zulip,dhcrzf/zulip,synicalsyntax/zulip,zulip/zulip,punchagan/zulip,tommyip/zulip,dhcrzf/zulip,rht/zulip,rishig/zulip,hackerkid/zulip,andersk/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,andersk/zulip,tommyip/zulip,showell/zulip,shubhamdhama/zulip,rht/zulip