fix flakiness from other prs

spec/02-integration/09-hybrid_mode/01-sync_spec.lua

@@ -260,20 +260,22 @@ describe("CP/DP communication #" .. strategy .. " inc_sync=" .. inc_sync, functi
         headers = {["Content-Type"] = "application/json"}
       }))
       assert.res_status(200, res)
-      -- as this is testing a negative behavior, there is no sure way to wait
-      -- this can probably be optimizted
-      ngx.sleep(2)
 
-      local proxy_client = helpers.http_client("127.0.0.1", 9002)
+      helpers.wait_until(function()
+        local proxy_client = helpers.http_client("127.0.0.1", 9002)
 
-      -- test route again
-      res = assert(proxy_client:send({
-        method  = "GET",
-        path    = "/soon-to-be-disabled",
-      }))
-      assert.res_status(404, res)
+        -- test route again
+        res = assert(proxy_client:send({
+          method  = "GET",
+          path    = "/soon-to-be-disabled",
+        }))
 
-      proxy_client:close()
+        local status = res and res.status
+        proxy_client:close()
+        if status == 404 then
+          return true
+        end
+      end)
     end)
 
     it('does not sync plugins on a route attached to a disabled service', function()