topic_list: Don't restore focus to search if it wasn't focused.
topic_list: Don't restore focus to search if it wasn't focused.

After topic list is updated, only restore focus to it, if it was
focused before. This avoids jumping focus from say compose box
to topic search unexpectedly when the topic list is updated.

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