* [CI] Make E2E tests run in multiple JDK versions

* Polish

* Use new e2e-container version number

* Install socat in reboot case

* Fix reboot case

* Polish

* Reorganize jobs

* Support upgrade backend w/o rebooting agents

* Override ES settings in FAQ

* Resend traffic data when invalid

* Remove unsupported ES setting

* Use seperated buffer directory and remove unnecessary web app 2

* Add e2e cluster tests