tests: Try to stabilize test_auto_leave_insert_mode

We sometimes tried to use hints before the page was fully rendered (?), thus
causing no elements to be found.

It also doesn't make much sense to test leaving insert mode if we aren't in
insert mode yet, so make sure we entered it first.

See #5390

tests/end2end/test_insert_mode.py

@@ -69,8 +69,11 @@ def test_auto_load_delayed_tab_close(quteproc):
 
 
 def test_auto_leave_insert_mode(quteproc):
+    quteproc.set_setting('input.insert_mode.auto_load', 'true')
+
     url_path = 'data/insert_mode_settings/html/autofocus.html'
     quteproc.open_path(url_path)
+    quteproc.wait_for(message='Entering mode KeyMode.insert (reason: *)')
 
     quteproc.set_setting('input.insert_mode.auto_leave', 'true')
     quteproc.send_cmd(':zoom 100')