upgrade-zulip: Extract shutdown call into a function.
upgrade-zulip: Extract shutdown call into a function.

This will help us call it as needed.

rht/zulip,andersk/zulip,brainwane/zulip,kou/zulip,brainwane/zulip,shubhamdhama/zulip,zulip/zulip,timabbott/zulip,synicalsyntax/zulip,hackerkid/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,synicalsyntax/zulip,hackerkid/zulip,timabbott/zulip,eeshangarg/zulip,zulip/zulip,kou/zulip,punchagan/zulip,shubhamdhama/zulip,eeshangarg/zulip,andersk/zulip,zulip/zulip,timabbott/zulip,zulip/zulip,eeshangarg/zulip,punchagan/zulip,timabbott/zulip,showell/zulip,shubhamdhama/zulip,hackerkid/zulip,andersk/zulip,shubhamdhama/zulip,rht/zulip,eeshangarg/zulip,punchagan/zulip,showell/zulip,punchagan/zulip,showell/zulip,shubhamdhama/zulip,timabbott/zulip,brainwane/zulip,shubhamdhama/zulip,brainwane/zulip,hackerkid/zulip,rht/zulip,kou/zulip,brainwane/zulip,rht/zulip,kou/zulip,synicalsyntax/zulip,eeshangarg/zulip,synicalsyntax/zulip,showell/zulip,timabbott/zulip,synicalsyntax/zulip,zulip/zulip,zulip/zulip,shubhamdhama/zulip,hackerkid/zulip,rht/zulip,eeshangarg/zulip,showell/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,brainwane/zulip,punchagan/zulip,synicalsyntax/zulip,rht/zulip,timabbott/zulip,synicalsyntax/zulip,punchagan/zulip,andersk/zulip,hackerkid/zulip,brainwane/zulip,showell/zulip,kou/zulip,kou/zulip,punchagan/zulip,showell/zulip,rht/zulip