Fix sessions not correcly loading untill a tab is focused

Summary:
A bit of frustration on my side: this is not the patch I want to
deliver, but I tried some other variants of this and nothing seemed
to work.
I tried:

• call setFocus() when the widget is created
• call session->run() (this froze konsole, fun times.)
• set the widget as current in the splitter.
  
  aparently forcing each widget to be displayed triggered something internally that made things work. I'm ok on removing this patch for a better one, but I'm out of ideas.

Reviewers: ngraham, Konsole, hindenburg

Reviewed By: ngraham, Konsole, hindenburg

Subscribers: konsole-devel

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D21216