do_update_message: Clean up timestamp code.
do_update_message: Clean up timestamp code.

By moving this logic to the topic of the functon, we make the code a
lot more readable.

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