Don't display the dev warning time when running self-update

Use the Application::find() method to resolve the command name, as Application::getCommandName() only returns whatever was entered as the first argument.
If the user only entered enough of the command to be unambiguous (eg self-up) then the warning would still show
By calling Application::find() we ensure that if we are going to run the self-update command then we will not show the warning, no matter what the user entered
Added some tests for the dev version warning
Merge pull request #3264 from duncan3dc/remove-self-update-warning

Don't display the dev warning time when running self-update