feedback_daemon: generate report right before sending

Feedback daemon used to generate report before waiting (for an hour by
default) until it's time to send it. Better actualize the reports and
generate them right when it's time to send them.

Part of #5750

src/box/lua/feedback_daemon.lua

@@ -333,16 +333,17 @@ local function feedback_loop(self)
     fiber.name(PREFIX, { truncate = true })
 
     while true do
-        local feedback = self:generate_feedback()
         local msg = self.control:get(self.interval)
         -- if msg == "send" then we simply send feedback
         if msg == "stop" then
             break
-        elseif feedback ~= nil then
-            if is_first_send then
-                fiber.sleep(10)
-                is_first_send = nil
-            end
+        end
+        if is_first_send then
+            fiber.sleep(10)
+            is_first_send = nil
+        end
+        local feedback = self:generate_feedback()
+        if feedback ~= nil then
             pcall(http.post, self.host, json.encode(feedback), {timeout=1})
         end
     end