Fix dir change when show hidden terminal panel with running program in it

Summary: Terminal panel doesn't change its working directory, while any procces is running in it. However, if you hide it and show again the program will get a string with a cd path command.

Test Plan:

1. Open dolphin
2. Press F4
3. Start any process like gnu nano
4. Press F4 two more times

Reviewers: Dolphin

Subscribers: anthonyfieroni, kfm-devel

Tags: Dolphin

Differential Revision: https://phabricator.kde.org/D22422