management/commands: Refactor logging code in register_server.
management/commands: Refactor logging code in register_server.

kou/zulip,rht/zulip,rht/zulip,andersk/zulip,zulip/zulip,andersk/zulip,andersk/zulip,andersk/zulip,zulip/zulip,andersk/zulip,kou/zulip,rht/zulip,rht/zulip,kou/zulip,kou/zulip,rht/zulip,zulip/zulip,zulip/zulip,zulip/zulip,andersk/zulip,andersk/zulip,kou/zulip,rht/zulip,zulip/zulip,rht/zulip,zulip/zulip,kou/zulip,kou/zulip