Add test case which publishes/subscribes 2mb message (#108)

* Add test case which publish/subscribes 2mb message

* Increase allowed package size for EMQ X

* Wait 45 seconds for broker to start

* Use default emqx.conf

* Try latest changes to EMQ X action

* Allow 3MB messages with EMQ X

* Revert "Try latest changes to EMQ X action"

This reverts commit 43f2058.

* Force latest version of namoshek/emqx-github-action