message view: Fix double loading indicator situation.
message view: Fix double loading indicator situation.

Since on narrowing we call `load_messages_for_narrow`,
which fetches both top and bottom messages, two loading
indicators were temporarily displayed.
This was also the case for the `home_msg_list` when we
call `mesage_fetch.initialize` on startup.

To resolve this we do not display the bottom loading
indicator (for new messages), if the older messages
are being fetched too. This is only for the initial
narrow change, and the bottom loading indicator will
be displayed correctly when the user is at the bottom.

This fixes a regression introduced when we added bottom loading
indicators at all, which was temporarily reverted in
67053ff479f01a4c7ee3423e8d99ecb98ccf0de1 before being restored in the
last couple commits.

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