js: Only trigger reload-on-focus once.
js: Only trigger reload-on-focus once.

We have observed infrequent storms of accesses (tens of thousands of
requests to minute) to `/` after an event queue expires.  The current
best theory is that the act of reloading the page itself triggers a
focus event, which itself triggers a reload before the prior one had
had time to do anything but send the network request.

Since the `focus` event here is merely as a backstop in case the
synchronous reloading and deferred reloading fail, we need only run it
once.

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