Fix broken tests in Travis CI

[mcgege]

Some test runs are still broken:

• centos-6
• rhel-6
• debian-6
• opensuse-leap-42
• sles-11
• sles-12

[artem-sidorenko]

Yes, I know, I know:-D

[mcgege]

Right now, all tests fail ... maybe it makes sense to upgrade this repo to the newest pdk template (#142) before fixing it?
And also on my wishlist: Include opensuse leap 42.3 + 15.0 :-)

[artem-sidorenko]

I'll have a look once I'm back from parental leave (end of September)

[mcgege]

Will be solved with #169